Optical diffraction component for suppressing at least one target wavelength by destructive interference

ABSTRACT

An optical diffraction component is configured to suppress at least one target wavelength by destructive interference. The optical diffraction component includes at least three diffraction structure levels that are assignable to at least two diffraction structure groups. A first of the diffraction structure groups is configured to suppress a first target wavelength λ 1 . A second of the diffraction structure groups is configured to suppress a second target wavelength λ 2 , where (λ 1 −λ 2 ) 2 /(λ 1 +λ 2 ) 2 &lt;20%. A topography of the diffraction structure levels can be described as a superimposition of two binary diffraction structure groups. Boundary regions between adjacent surface sections of each of the binary diffraction structure groups have a linear course and are superimposed on one another at most along sections of the linear course.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application claims the priorities of German patentapplication DE 10 2019 200 376.1, filed Jan. 15, 2019, and DE 10 2019210 450.9, filed Jul. 16, 2019, the contents of which are incorporatedby reference herein.

FIELD

The disclosure relates to an optical diffraction component forsuppressing at least one target wavelength by destructive interference.Furthermore, the disclosure relates to an EUV collector of a projectionexposure apparatus including such an optical diffraction component, anillumination system including such an EUV collector, an optical systemincluding such an illumination system, a projection exposure apparatusincluding such an optical system, and a method for producing astructured component with the aid of such a projection exposureapparatus, and a structured component produced in this way.

BACKGROUND

An EUV collector including an optical diffraction component in the formof an optical grating is known from WO 2017/207401 A1 and from WO2014/114405 A2. Embodiments of optical gratings for suppressing IRwavelengths in EUV projection exposure apparatuses are known from thepublication “Multilayer EUV optics with integrated IR-suppressiongratings”, T. Feigl et al., 2016 EUVL Workshop, Berkeley, Jun. 13-16,2016. EP 1 540 423 B1 describes a grating-based spectral filter forsuppressing radiation outside a used band in an EUV lithography system.US 2014/0131586 A1 describes a phase grating for a mask inspectionsystem. DE 10 2009 044 462 A1 describes an optical filter elementincluding a grating structure for diffracting infrared radiation withinan EUV illumination system. The technical article “Multilevel blazedgratings in resonance domain: an alternative to the classicalfabrication approach” by M. Oliva et al., OPTICS EXPRESS, Vol. 19, No.15, 2011, pages 1473 to 1475, and the technical article “Highlyefficient three-level blazed grating in the resonance domain” by M.Oliva et al., OPTICS LETTERS Vol. 35, No. 16, 2010, pages 2774 to 2776,describe different variants of blazed gratings. The technical article“Diffractive elements designed to suppress unwanted zeroth order due tosurface depth error” by V. Kettunen et al., Journal of Modern Optics 51,14, 2111-2123, 2004, discloses diffractive elements for suppressingunwanted zero orders of diffraction on account of a profile depth error.

DE 195 16 741 A1 discloses a diffraction-optically effective structurearrangement. DE 100 54 503 A1 discloses a light-diffracting binarygrating structure. WO 2007/031 992 A1 discloses a diffraction gratinghaving a spatially changing duty cycle.

An optical grating can be used for suppressing stray light of awavelength that deviates from that of used light. The stray light canthen be diffracted by the optical grating towards a light trap (beamdump), whereas used light takes a different path.

SUMMARY

The present disclosure seeks to provide an optical diffraction componentfor suppressing at least one target wavelength by destructiveinterference so that the possibilities for use thereof are extended inparticular for stray light suppression.

In a first general aspect, the disclosure provides an opticaldiffraction component that includes a periodic grating structure profileincluding diffraction structures, having three diffraction structurelevels, which predefine different structure depths relative to areference plane. The arrangement of the diffraction structures is suchthat a wavelength range around a first target wavelength λ₁ in theinfrared wavelength range, which first target wavelength is diffractedby the grating structure profile, has radiation components having atleast three different phases which interfere with one anotherdestructively at least in the zero and/or +/− first order(s) ofdiffraction of the first target wavelength λ₁. The diffraction structurelevels predefine a topography of a grating period of the gratingstructure profile that is repeated regularly along a period runningdirection. The diffraction structure levels include: a neutraldiffraction structure level, which corresponds to a reference height ofzero; a positive diffraction structure level, which is arranged higherby an optical path length of λ₁/4+/−20% relative to the neutraldiffraction, structure level; and a negative diffraction structurelevel, which is arranged lower by an optical path length of λ₁/4+/−20%relative to the neutral diffraction structure level.

A range to be suppressed around the target wavelength λ₁ can be chosenso as to encompass a plurality of wavelengths to be suppressed, forexample the different wavelengths of a prepulse and of a main pulse ofan EUV plasma light source.

In the case of the optical diffraction component in accordance with thefirst aspect, firstly the positive diffraction structure level andsecondly the negative diffraction structure level are embodied with atolerance range of a maximum of 20% around the optical path lengthdifference of λ₁/4 relative to the neutral diffraction structure level.This tolerance in comparison with the path length difference λ₁/4 canalso be less than +/−20% and can be for example +/−15%, +/−10%, +/−5%,+/−4%, +/−3%, +/−2%, or even +/−1%.

In the case of the optical diffraction component according to the firstaspect, a grating period of the grating structure profile can besubdivided into four period sections of the diffraction structurelevels. Two of the four period sections can be embodied as neutraldiffraction structure sections having the neutral diffraction structurelevel. One of the four period sections can be embodied as a positivediffraction structure section having the positive diffraction structurelevel. One of the four period sections can be embodied as a negativediffraction structure section having the negative diffraction structurelevel. In the case of this embodiment of the optical diffractioncomponent, the two neutral diffraction structure levels can be arrangedin the grating period in a manner separated from one another by apositive diffraction structure level or by a negative diffractionstructure level. The separation of the two neutral diffraction structurelevels from one another enables a sequence of the diffraction structurelevels in which in the period running direction an identical number offalling edges or sidewalls (structure depth increases, edge“valley-wards”) and rising edges or sidewalls (structure depth decreasesagain, edge “peakwards”) having in each case mutually comparablestructure height differences are present. Firstly the falling edges andsecondly the rising edges then respectively compensate for one anotheras far as a possible phase error is concerned, with the result that anentire phase error, possibly stemming from an undesired edge structuringand/or an undesired edge position, is reduced or wholly avoided.

Alternatively, the two neutral diffraction structure levels can also bearranged directly successively in the grating period as a neutraldiffraction structure level of double length.

The four period sections into which the grating period of the gratingstructure profile can be subdivided can have an identical length alongthe period running direction, wherein an identical length is present ifthe lengths differ from one another by less than +/−20%. Such an opticaldiffraction component gives rise to a particularly good destructivelyinterfering suppressing effect for the target wavelength. The lengths ofthe four period sections can deviate from one another by less than 20%,for example by less than 15%, by less than 10%, by less than 5%, by lessthan 4%, by less than 3%, by less than 2% or even by less than 1%. Thelengths of the four period sections can also be exactly identical.

The four period sections into which the grating period of the gratingstructure profile can be subdivided can have the following sequence:positive diffraction structure level, neutral diffraction structurelevel, negative diffraction structure level, neutral diffractionstructure level. Such a sequence of the period sections has been foundto be particularly suitable. A corresponding sequence is achievable bycyclically interchanging the sequence indicated above, thus resulting inthe following sequence, for example: neutral diffraction structurelevel, positive diffraction structure level, neutral diffractionstructure level, negative diffraction structure level.

The following sequence of the four period sections is also possible:Negative diffraction structure level, neutral diffraction structurelevel, positive diffraction structure level, neutral diffractionstructure level. Cyclic interchange is possible in the case of thisvariant, too.

The following can be used as a further variant of the sequence of thefour period sections: Neutral diffraction structure level, neutraldiffraction structure level; positive diffraction structure level,negative diffraction structure level. Here, therefore, two neutraldiffraction structure levels are present directly next to one another asa common neutral diffraction structure level in particular of doublelength. Cyclic interchange, for example, is possible in the case of thisvariant, too.

In the case of the optical diffraction component in accordance with thefirst aspect, the arrangement of the diffraction structures can be suchthat a target wavelength range, containing the target wavelength, in theinfrared wavelength range, which is diffracted by the grating structureprofile, has radiation components having at least three different phaseswhich interfere with one another destructively at least in the zeroand/or +/− first order(s) of diffraction of the first target wavelength,wherein the target wavelength range also includes, besides the firsttarget wavelength λ₁, a second target wavelength λ₂ different therefrom,wherein the arrangement of the diffraction structures is such that awavelength range around the second target wavelength in the infraredwavelength range, which is diffracted by the grating structure profile,also has radiation components having at least three different phaseswhich interfere with one another destructively at least in the zeroand/or +/− first order(s) of diffraction of the first target wavelength,wherein the target wavelength range also includes, besides the firsttarget wavelength, a target wavelength different therefrom, wherein thearrangement of the diffraction structures is such that a wavelengthrange around the second target wavelength in the infrared wavelengthrange, which is diffracted by the grating structure profile, hasradiation components having at least three different phases whichinterfere with one another destructively at least in the zero and/or +/−first order(s) of diffraction of the second target wavelength, whereinfor the two target wavelengths λ₁ and λ₂ it holds true that:(λ₁−λ₂)²/(λ₁+λ₂)²<20%. The advantages of such an optical diffractioncomponent correspond to those which have already been explained above.

For the upper limit value characterizing the difference between the twotarget wavelengths, it can hold true that: (λ₁−λ₂)²/(λ₁+λ₂)²<15%, 10%,<5%, <4%, <3%, <2%, <1%, <0.5%, <0.2%, <0.1%, <0.05%, <0.01%, <0.001%.The upper limit value can be 0.037%, for example. The upper limit valuecan also be significantly smaller still, for example 0.0002%. The twotarget wavelengths that are suppressed by the at least two diffractionstructure groups of the optical diffraction component can be exactlyidentical. A deviation (λ₁−λ₂)²/(λ₁+λ₂)² characterizing the differencebetween the two target wavelengths can be greater than 0.0001%, can begreater than 0.001%, can be greater than 0.01%, can be greater than0.1%, can be greater than 0.2%, can be greater than 0.5%, can be greaterthan 0.7% and can also be even greater.

The target wavelengths can be in the IR wavelength range, for example inthe range of the typical emission wavelengths of CO₂ lasers at 10.6 μm.Alternatively or additionally, wavelengths in the NIR wavelength range,in the visible wavelength range, in the UV wavelength range or else inthe DUV wavelength range can constitute target wavelengths to besuppressed. One of the two target wavelengths can be 10.2 μm and theother of the two target wavelengths can be 10.6 μm. The targetwavelengths can be adapted to the wavelengths of a prepulse and of amain pulse of an EUV plasma light source.

The design of the at least two diffraction structure groups forsuppressing two different target wavelengths results in a suppression ofwavelengths within a predefinable wavelength bandwidth, which can alsobe referred to as suppression design bandwidth. Wavelengths which liewithin this suppression design bandwidth, that is to say which can beeffectively suppressed by the optical diffraction component, cancorrespond to the target wavelengths and/or can lie between the targetwavelengths and/or can lie outside a wavelength range between the targetwavelengths. For suppressing a wavelength of 10.2 μm, by way of example,a first target wavelength, for which the first diffraction structuregroup is designed, can be 10.25 μm and a second target wavelength, forwhich the second diffraction structure group is designed, can be 10.55μm. The choice of the target wavelengths arises depending on the desiredproperties of the optical diffraction component for suppressingoptionally a plurality of different wavelengths or wavelengthbandwidths. In this case, a position of further minima of destructiveinterference besides the target wavelengths can also be taken intoaccount or it is possible to take account of which wavelengths aredeliberately intended not to be suppressed.

What has already been discussed above in association with the opticaldiffraction component can hold true here for the choice of the targetwavelengths λ₁ and λ₂.

In a second general aspect, the disclosure provides an opticaldiffraction component for suppressing at least one target wavelength bydestructive interference. The component includes at least threediffraction structure levels which predefine different structure depthsrelative to a reference plane. The three diffraction structure levelsare assignable to at least two diffraction structure groups. A first ofthe diffraction structure groups is embodied for suppressing a firsttarget wavelength λ₁ in the zero order of diffraction. A second of thediffraction structure groups is embodied for suppressing a second targetwavelength λ₂ in the zero order of diffraction. The two targetwavelengths λ₁ and λ₂ are such that: a topography of the diffractionstructure levels can be described as a superimposition of two binarydiffraction structure groups wherein each of the binary diffractionstructure groups has: first surface sections having a first structuredepth; and second surface sections having a second structure depth,which alternate with the first surface sections along a runningdirection. Boundary regions between adjacent surface sections of each ofthe binary diffraction structure groups have a linear course, whereinfirst boundary regions of the first of the two binary diffractionstructure groups, second boundary regions of the second of the twobinary diffraction structure groups, and they are superimposed on oneanother at most along sections of their linear course.

Use of an optical diffraction component including at least threediffraction structure levels which are in turn assignable to at leasttwo diffraction structure groups which serve for suppressing respectivetarget wavelengths that are not too far apart from one anothersurprisingly results in an improvement in a suppression of the targetwavelength which distinctly goes beyond the suppression effect of theindividual diffraction structure groups. In comparison with opticaldiffraction components from the prior art, this results in degrees offreedom of design which can be used to enhance the flexibility of thepossibilities for use of the optical diffraction component. Thedifferent diffraction structure groups can occupy the same opticallyused area of the optical diffraction component, that is to say do nothave to be arranged on mutually separate sections on the optically usedarea. The optical diffraction component can be designed in particularsuch that the two diffraction structure groups are designed forsuppressing the same target wavelength or stray light wavelength.Alternatively or additionally, the optical diffraction component can bedesigned for suppressing a plurality of target wavelengths withappropriate design of the diffraction structure groups. In the case ofsuch an optical diffraction component including a plurality ofdiffraction structure groups, it has been found that a diffractiveeffect is improved in comparison with an optical diffraction componentincluding exactly one diffraction structure group. With the use of theoptical diffraction component including a plurality of diffractionstructure groups, the same suppressing effect can thus be achieved withrelaxed manufacturing tolerances in comparison with the prior art.

A diffraction structure group is an arrangement of at least twodiffraction structure levels which are arranged and fashioned forsuppressing exactly one target wavelength. One example of a diffractionstructure group is an optical grating. The assignment of the at leastthree diffraction structure levels to at least two diffraction structuregroups is regularly such that at least one diffraction structure levelis assigned to a plurality of diffraction structure groups.

The optical diffraction component according to the first aspectdiscussed initially can also include at least one or else at least twodiffraction structure groups of this type.

The advantages regarding the maximum difference between the two targetwavelengths correspond to those which have already been explained above.What has already been discussed above in association with the opticaldiffraction component according to the first aspect can be asserted herefor the choice of the target wavelengths λ₁ and λ₂.

For the second target wavelength λ₂, too, it holds true that the latteris attenuated or suppressed by destructive interference on account of anappropriate design of diffraction structures of the optical diffractioncomponent.

The optical diffraction component can include exactly three diffractionstructure levels and can include exactly two diffraction structuregroups. Alternatively, the optical diffraction component can alsoinclude more than three diffraction structure levels, for example four,five, six or even more diffraction structure levels, and correspondinglyalso more than two diffraction structure groups.

A binary structure is a structure including positive structures(“peaks”) and negative structures (“valleys”), wherein the total area ofthe positive structures corresponds to the total area of the negativestructures within predefined tolerances. A difference between the totalareas firstly of the positive structures and secondly of the negativestructures can be less than 20%, can be less than 10%, can be less than5%, can be less than 4%, can be less than 3%, can be less than 2% andcan also be less than 1%. The total areas can also be exactly identical.

The fact that the boundary regions of the first and second binarystructures are superimposed on one another at most along sections of thelinear course of the boundary regions affords the possibility ofproducing the optical diffraction component with the aid ofcomparatively simply fashioned lithographic mask structures. Thisaffords the possibility of precise production of the optical diffractioncomponent with compliance with narrow tolerances firstly for the areasof the diffraction structure levels and also for the structure depthsthereof. In particular, it is possible to produce diffraction structuregroups having desirably great and desirably precise sidewall steepnessof the boundary regions.

The optical diffraction component can be fashioned such that a risingboundary region, that is to say a rising level sidewall, is assigned afalling boundary region with the same structure depth, that is to saythe same structure height difference.

The optical diffraction component according to the second aspect canadditionally have features which have already been discussed above.

In the case of the optical diffraction component, the first boundaryregions of the first of the two binary diffraction structure groups andthe second boundary regions of the second of the two binary diffractionstructure groups can run completely separately from one another. Such acompletely separated course of the boundary regions results in a furthersimplification in particular of lithographic production of the opticaldiffraction component.

A first of the diffraction structure groups can be embodied as a firstdiffraction grating arranged on a grating surface. The first diffractiongrating can have a first grating period and a first structure depth,measured as optical path difference between first diffraction positivestructures and first diffraction negative structures perpendicular to asurface section of the grating surface that respectively surrounds thesefirst structures. A second of the diffraction structure groups can beembodied as a second diffraction grating arranged on the gratingsurface. Such a second diffraction grating can have a second gratingperiod and a second structure depth, measured as optical path differencebetween second diffraction positive structures and second diffractionnegative structures perpendicular to a surface section of the gratingsurface that respectively surrounds these second structures. With regardto such an embodiment, the use of an optical grating including at leasttwo diffraction gratings having grating periods that are fundamentallyindependent of one another and structure depths that are fundamentallyindependent of one another, wherein the structure depth is smallcompared with the grating period at least in the case of one of thediffraction gratings, results, in comparison with optical gratings ofthe prior art, in degrees of freedom of design which can be used toenhance the flexibility of the possibilities for use of the opticalgrating. The two diffraction gratings can occupy the same gratingsurface, that is to say are then not arranged on separate sections onthe grating surface. The two diffraction gratings are then present,therefore, in a manner being superimposed on one another on the gratingsurface. The optical grating can be designed such that its stray lightsuppression is improved by virtue of the two diffraction gratings beingdesigned for suppressing identical stray light wavelengths.Alternatively or additionally, the optical grating can be designed suchthat a plurality of stray light wavelengths can be suppressed. It hassurprisingly been found, moreover, that with the use of such an opticalgrating including a plurality of diffraction gratings, a diffractiveeffect, in particular a suppressing effect as a result of destructiveinterference in the zero order of diffraction, is improved in comparisonwith an optical grating including exactly one diffraction grating. Thesame suppressing effect can thus be achieved with relaxed manufacturingtolerances with the use of the optical grating including a plurality ofdiffraction gratings.

The optical grating can be embodied as a reflection grating, but canalternatively also be embodied as a transmission grating, and forexample as a phase grating.

The grating surface can be embodied as plane or else curved, e.g. convexor concave. The grating surface can be part of an optical surface of anoptical component which additionally has some other optical function,for example on a beam collector or a mirror. The first diffractiongrating and/or the second diffraction grating can be embodied as abinary grating in which a surface area of the positive structures isequal to a surface area of the negative structures. In the simplestcase, the structure depth can be the height difference between therespective diffraction positive structures and the associateddiffraction negative structures.

The optical grating can additionally bear a highly reflective layer andoptionally auxiliary layers, in particular for protecting the opticalgrating and/or the highly reflective layer. The highly reflective layercan be embodied as a multilayer. The highly reflective layer can beembodied for EUV light in a wavelength range of, in particular, between5 nm and 30 nm.

The optical diffraction component can be embodied as a multileveldiffraction grating having correspondingly arranged diffractionstructure levels.

In this case, a structure depth can be one sixth of the targetwavelength. With the multilevel grating being fashioned accordingly, astructure depth can also be one quarter of the target wavelength.

Depending on a number m of the different diffraction structure levels, astructure depth depending on the target wavelength λ_(N) can be:b=λ_(N)/(2 m).

A grating period can be in the millimetres range and can be for example1 mm or 2 mm.

The diffraction structure levels can be embodied as plane surfaces.

The grating periods of the different diffraction gratings can be in anintegral ratio to one another. The grating periods can have a definedphase offset with respect to one another.

A ratio of the grating periods can be 1:2. With the use of threediffraction gratings, the ratio of the grating periods can be 1:2:4 orelse 1:2:2.

A surface area ratio of surface areas of the first diffraction positivestructures to surface areas of the first diffraction negative structurescan be in the range of between 0.9 and 1.1 (e.g., 0.9, 0.95, 1, 1.05,1.1). A surface area ratio of surface areas of the second diffractionpositive structures to surface areas of the second diffraction negativestructures can be in the range of between (e.g., 0.9, 0.95, 1, 1.05,1.1). Correspondingly precise binary diffraction structure groupsresult.

A ratio between the first grating period and the first structure depthcan be greater than 10. A ratio between the second grating period andthe second structure depth can be greater than 10.

Correspondingly different target wavelengths to be suppressed result.Besides the two target wavelengths λ₁ and λ₂, a further, more greatlydeviating target wavelength can thus also be suppressed. By way ofexample, it is possible simultaneously to suppress different targetwavelengths in the infrared wavelength range and a further targetwavelength in the ultraviolet wavelength range.

A period ratio of the first grating period to the second grating periodcan be in the range of between 0.9 and 1.1 (e.g., 0.9, 0.95, 1, 1.05,1.1).

An optical diffraction component having such a period ratio can bemanufactured well. The grating periods of the first and seconddiffraction gratings can be exactly equal, but can also be different.

The advantages of such an optical diffraction component make possible,in conjunction with good reflection conditions in particular for EUVwavelengths, a good stray light suppression of higher wavelengthsincluding in the case of the second diffraction grating.

A structure depth ratio of the structure depth of the first diffractiongrating to the structure depth of the second diffraction grating can bein the range of between 0.9 and 1.1 (e.g., 0.9, 0.95, 1, 1.05, 1.1). Thestructure depths of the first and second diffraction gratings can bedifferent from one another, but can also be equal. A significantlylarger structure depth ratio between the two diffraction gratings in therange of between 1.1 and 20 is also possible, for example a structuredepth ratio in the region of 10.

In the case of the optical diffraction component including the twodiffraction gratings arranged on a grating surface, the first gratingperiod can run along a first period running direction of the firstdiffraction grating and the second grating period can run along a secondperiod running direction of the second diffraction grating, wherein thetwo period running directions cannot run parallel to one another. Suchan optical diffraction component in which the period running directionsof the first and second diffraction gratings do not run parallel to oneanother has proved to be worthwhile. A smallest angle between the periodrunning directions can be 90°, such that the two period runningdirections are perpendicular to one another. A smaller smallest angle,for example in the region of 60°, 55°, 45° or 30°, is also possible.

Alternatively, an embodiment of the optical diffraction component inwhich the two period running directions of the at least two diffractionstructure groups run parallel to one another is also possible.

The optical diffraction component including the two diffraction gratingsarranged on the grating surface can include at least one furtherdiffraction grating arranged on the grating surface. The furtherdiffraction grating can include further diffraction positive structuresand further diffraction negative structures, wherein a surface arearatio of surface areas of the further diffraction positive structures tosurface areas of the further diffraction negative structures is in therange of between 0.9 and 1.1 (e.g., 0.9, 0.95, 1, 1.05, 1.1). Thefurther diffraction grating has a further grating period and a furtherstructure depth, which is measured as optical path difference betweenthe further diffraction positive structures and the further diffractionnegative structures perpendicular to a surface section of the gratingsurface that respectively surrounds these further structures. Such anoptical diffraction component including at least one further diffractiongrating results in a corresponding further increase in the availabledegrees of freedom of design. At least two of the period runningdirections of the at least three diffraction gratings can have mutuallydifferent directions. Alternatively, it is also possible for all theperiod running directions of the at least three diffraction gratings torun parallel to one another.

In the case of the optical diffraction component including the firstdiffraction grating, the second diffraction grating and the furtherdiffraction grating all arranged on the grating surface, a ratio betweenthe further grating period and the further structure depth can begreater than 10. A period ratio of the first grating period to thefurther grating period can be in the range of between 0.9 and 1.1 (e.g.,0.9, 0.95, 1, 1.05, 1.1). The first grating period can run along a firstperiod running direction of the first diffraction grating and thefurther grating period can run along a further period running directionof the further diffraction grating, wherein the two period runningdirections do not run parallel to one another.

The advantages of such an optical diffraction component correspond tothose which have already been explained above. The grating periods ofthe first diffraction grating and of the further diffraction grating canbe identical, but can also be different. Corresponding period ratios inthe range of between 0.9 and 1.1 (e.g., 0.9, 0.95, 1.05, 1.1) or elseidentical grating periods can also be present between the seconddiffraction grating and the at least one further diffraction grating.

A structure depth ratio of the first diffraction grating with respect tothe further diffraction grating can be in the range of between 0.9 and1.1 (e.g., 0.9, 0.95, 1.05, 1.1); structure depths of the first andfurther diffraction gratings can be different from one another, but canalso be equal. Corresponding structure depth ratios in the range ofbetween 0.9 and 1.1 (e.g., 0.9, 0.95, 1.05, 1.1) or else identicalstructure depths can also be present between the second diffractiongrating and the at least one further diffraction grating. Asignificantly greater structure depth ratio between the structure depthsof the further diffraction grating and the first and/or seconddiffraction grating in the range of between 1.1 and 20, for example inthe region of 10, is also possible.

A smallest angle between the period running directions of the firstdiffraction grating and the further diffraction grating can be in therange of between 20° and 25°. Some other smallest angle e.g. in therange of between 10° and 80° is also possible. Corresponding runningdirection angles can also be present between a period running directionof the second diffraction grating and the period running direction ofthe at least one further diffraction grating.

The surface areas of the diffraction positive structures and of thediffraction negative structures of the various diffraction structuregroups can make identical contributions to the entire grating surface.Such identical surface area contributions yield, in particular, binarygratings for the different diffraction structure groups of the opticaldiffraction component. This ensures a high stray light suppression inthe region of the zero order of diffraction in the case of appropriatedesign of the optical diffraction component.

The above-discussed features of the optical diffraction components ofthe two aspects can also be combined with one another.

The optical diffraction component of the type of at least one of the twoaspects discussed above can be produced by a mask etching method inwhich at least one mask structure is used. A plurality of maskstructures can also be used, which differ in the positions of their maskregions and/or their mask gaps. A substrate can then be etched withsequential use of these different masks or by displacement of one andthe same mask structure in at least two sequential etching steps. Threeor more different mask structures can also be used in such a masketching method for producing the optical diffraction component.

The advantages of a collector or a collector mirror which can be used ina projection exposure apparatus, and in particular in an EUV projectionexposure apparatus, and has an optical diffraction component having theproperties described above correspond to those which have already beenexplained above with reference to the optical diffraction component.These advantages are evident particularly in the case of use inassociation with an EUV light source in which plasma is produced bylaser-induced discharge. The collector or the collector mirror can be anEUV collector/collector mirror for a wavelength range of, in particular,between 5 nm and 30 nm and/or a DUV (Deep UltraViolet)collector/collector mirror, that is to say a collector mirror for awavelength range of, in particular, between 150 nm and 250 nm.

This applies particularly to an EUV collector mirror in which thecollector mirror is embodied in such a way that it guides EUV radiationtowards a focal region, wherein the optical diffraction component isembodied in such a way that it guides the radiation of the at least onetarget wavelength away from the focal region. The radiation of the atleast one target wavelength is also referred to as stray light.

An illumination system can include such a collector, in particular anEUV collector, and an illumination optical unit for illuminating anobject field, in which an object to be imaged is arrangeable. DUV or EUVused light can be used as illumination light. The advantages of such anillumination system correspond to those that have already been explainedabove with reference to the collector according to the invention. Theused light is precisely not suppressed by the optical diffractioncomponent, that is to say has a different wavelength from that of straylight to be suppressed.

The illumination system can be fashioned with the optical diffractioncomponent embodied as described above so as to result in a homogeneousdistribution of the stray light in the region of stray light removallocations and for example in the region of beam dumps provided for thispurpose. Alternatively or additionally, it is possible to ensure apredefined distribution function of the used light in particular inspecific sections of an illumination beam path of the illuminationsystem, for example in the region of a pupil plane.

An optical system can include such an illumination system and aprojection optical unit for imaging the object field into an imagefield, wherein a substrate is arrangeable in the image field, andwherein a section of the object to be imaged is able to be imaged ontothe substrate. A projection exposure apparatus can include such anoptical system and a light source, in particular an EUV light source. Inorder to produce a structured component, a reticle and a wafer can beprovided. A structure on the reticle can be projected onto alight-sensitive layer of the wafer with the aid of such a projectionexposure apparatus. With this approach, it is possible to produce amicrostructure and/or nanostructure on the wafer. The advantages of suchan optical system, of such a projection exposure apparatus, of such aproduction method and of such a microstructured and/or nanostructuredcomponent correspond to those which have already been explained abovewith reference to the collector according to the invention.

Insofar as an EUV light source is used, it can include a pump lightsource for producing a plasma that generates EUV wavelengths. The pumplight source can be embodied for producing a prepulse having a prepulselight wavelength and for producing a main pulse having a main pulselight source. The prepulse light wavelength can differ from the mainpulse wavelength. Corresponding differences between the wavelengthsfirstly of the prepulse light and secondly of the main pulse light inthe case of the pump light source of the EUV light source of theprojection exposure apparatus can have upper and/or lower limit valueswhich have already been explained above in association with the targetwavelengths λ₁ and λ₂.

In particular, a semiconductor component, for example a memory chip, canbe produced using the projection exposure apparatus.

In a general aspect, a component, includes a periodic grating structureprofile including diffraction structures configured so that a wavelengthrange around a first wavelength, λ₁, is diffracted by the periodicgrating structure profile. The first wavelength, λ₁, is in the infraredwavelength range. The wavelength range includes radiation componentsincluding at least three different phases which interfere with eachother destructively in at least one order of diffraction. The at leastone order of diffraction is selected from the group consisting of: thezero order of diffraction of the first wavelength, λ₁; the + first orderof diffraction of the first wavelength, λ₁; and the − first order ofdiffraction of the first wavelength, λ₁. The diffraction structuresinclude diffraction structure levels. The diffraction structure levelsinclude: a neutral diffraction structure level corresponding to areference height of zero; a positive diffraction structure levelarranged higher by an optical path length of λ₁/4+/−20% relative to theneutral diffraction structure level; and a negative diffractionstructure level arranged lower by an optical path length of λ₁/4+/−20%relative to the neutral diffraction structure level. The diffractionstructure levels define a topography of a grating period of a gratingstructure profile that is repeated regularly along a direction.

The grating period can include at least one neutral diffractionstructure section having the neutral diffraction structure level. Thegrating period can include two neutral diffraction structure sectionshaving the neutral diffraction structure level. The grating period caninclude a positive diffraction structure section having the positivediffraction structure level. The grating period can include a positivediffraction structure section having the negative diffraction structurelevel. The grating period can include: a first neutral diffractionstructure section having the neutral diffraction structure level; asecond neutral diffraction structure section having the neutraldiffraction structure level; a positive diffraction structure sectionhaving the positive diffraction level; and a negative diffractionstructure section having the negative diffraction structure level. Thediffraction structure sections have the following sequence: the positivediffraction structure level; the first neutral diffraction structurelevel; the negative diffraction structure level; and the second neutraldiffraction structure level.

Along the direction, the diffraction structure sections have the samelength within +/−20% (e.g., within +/−15%, within +/−10%, within +/−5%,within +/−4%, within +/−3%, within +/−2%, within +/−1%).

The wavelength range can further include a second wavelength, λ₂,wherein: the wavelength, λ₂, is different from the first wavelength, λ₁;and the second wavelength, λ₂, is in the infrared wavelength range. Thediffraction structures can be configured so that the wavelength rangefurther includes radiation components including at least threeadditional different phases which interfere with each otherdestructively in at least one order of diffraction selected from thegroup consisting of: the zero order of diffraction of the firstwavelength, λ₂; the + first order of diffraction of the firstwavelength, λ₂; and the − first order of diffraction of the firstwavelength, λ₂. In some embodiments, (λ₁−λ₂)²/+λ₂)²<20% (e.g., <15%,<10%, <5%, <4%, <3%, <2%, <1%, <0.5%, <0.2%, <0.1%, <0.05%, <0.01%,<0.001%, <0.0002%). Optionally, in such embodiments,(λ₁−λ₂)²/(λ₁+λ₂)²>0.0001% (e.g., >0.001%, >0.01%, >0.1%, >0.5%, >0.7%).The wavelength range can include radiation components including at leastthree different phases which interfere with one each other destructivelyin the zero order of diffraction of the first wavelength, λ₂. Thewavelength range can include radiation components including at leastthree different phases which interfere with one each other destructivelyin the + first order of diffraction of the first wavelength, λ₂. Thewavelength range can include radiation components including at leastthree different phases which interfere with one each other destructivelyin the − first order of diffraction of the first wavelength, λ₂.

The wavelength range can include radiation components including at leastthree different phases which interfere with one each other destructivelyin the zero order of diffraction of the first wavelength, λ₁. Thewavelength range can include radiation components including at leastthree different phases which interfere with one each other destructivelyin the + first order of diffraction of the first wavelength, λ₁. Thewavelength range can include radiation components including at leastthree different phases which interfere with one each other destructivelyin the − first order of diffraction of the first wavelength, λ₁.

The positive diffraction structure level can be higher by an opticalpath length of λ₁/4+/−15% (e.g., +/−10%, +/−5%, +/−4%, +/−3%, +/−2%,+/−1%) relative to the neutral diffraction structure level.

The negative diffraction structure level can lower by an optical pathlength of λ₁/4+/−15% (e.g., +/−10%, +/−5%, +/−4%, +/−3%, +/−2%, +/−1%)relative to the neutral diffraction structure level.

In a general aspect, the disclosure provides a component that includesat least three diffraction structure levels defining different structuredepths relative to a reference plane. The three diffraction structurelevels are assignable to at least first and second diffraction structuregroups. The first diffraction structure group is configured to suppressthe zero order of diffraction of a first wavelength, λ₁. The seconddiffraction structure group is configured to suppress the zero order ofdiffraction of a second wavelength, λ₂. (λ₁−λ₂)²/(λ₁+λ₂)²<20%. Atopography of the diffraction structure levels includes asuperimposition of first and second binary diffraction structure groups.For each of the first and second binary diffraction structure groups:the binary diffraction structure group includes first surface sectionshaving a first structure depth and second surface sections having asecond structure depth; and the first and second surface sectionsalternate along a direction. Boundary regions between adjacent surfacesections of the first and second binary diffraction structure groupshave a linear course. Boundary regions of the first binary diffractionstructure group and boundary regions of the second binary diffractionstructure group are superimposed on each other at most along sections oftheir linear course.

The boundary regions of the first binary diffraction structure group andthe boundary regions of the second diffraction structure group can runcompletely separately from one another.

The boundary regions of the first binary diffraction structure group andboundary regions of the second binary diffraction structure group can besuperimposed on each other.

The first diffraction structure group can include a first diffractiongrating supported by a grating surface. The first diffraction gratingcan have a first grating period. The first diffraction grating caninclude first diffraction positive structures and first diffractionnegative structures. The first diffraction positive structures can beperpendicular to a section of the grating surface surrounding the firstdiffraction positive structures. The first diffraction negativestructures can be perpendicular to a section of the grating surfacesurrounding the first diffraction negative structures. The firstdiffraction grating can have a first structure depth that is an opticalpath difference between the first diffraction positive structures andthe first diffraction negative structures. The second diffractionstructure group can include a second diffraction grating supported bythe grating surface. The second diffraction grating can have a secondgrating period. The second diffraction grating can include seconddiffraction positive structures and second diffraction negativestructures. The second diffraction positive structures can beperpendicular to a section of the grating surface surrounding the seconddiffraction positive structures. The second diffraction negativestructures can be perpendicular to a section of the grating surfacesurrounding the second diffraction negative structures. The seconddiffraction grating can have a second structure depth that is an opticalpath difference between the second diffraction positive structures andthe second diffraction negative structures. The first grating period canalong a direction that is not parallel to a direction along which thesecond grating period runs.

The component can be configured so that, for the first and seconddiffraction gratings, surface areas of the diffraction positivestructures and of the diffraction negative structures make identicalcontributions to the entire grating surface. The component can beconfigured so that, for the first and second diffraction gratings,surface areas of the diffraction positive structures and of thediffraction negative structures make contributions to the entire gratingsurface that differ by at most 20% (e.g., at most 10%, at most 5%, atmost 4%, at most 3%, at most 2%, at most 1%) from each other.

The component can further include a third diffraction grating supportedby the grating surface. The following may hold: the third diffractiongrating includes third diffraction positive structures and thirddiffraction negative structures; the third diffraction grating has athird grating period; the third diffraction positive structures areperpendicular to a section of the grating surface surrounding the thirddiffraction positive structures; the third diffraction negativestructures are perpendicular to a section of the grating surfacesurrounding the third diffraction negative structures; the thirddiffraction grating has a third structure depth that is an optical pathdifference between the third diffraction positive structures and thethird diffraction negative structures. A ratio of surface areas of thethird diffraction positive structures to surface areas of the thirddiffraction negative structures can be between 0.9 and 1.1 (e.g., 0.9,0.95, 1, 1.05, 1.1). A ratio of the third grating period to the thirdstructure depth can be greater than 10. A ratio of the first gratingperiod to the third grating period can be between 0.9 and 1.1 (e.g.,0.9, 0.95, 1, 1.05, 1.1).

The first grating period can run along a direction that is not parallelto a direction along which the third grating period runs.

The component can be configured so that, for at each of at least two ofthe diffraction gratings, surface areas of the diffraction positivestructures and of the diffraction negative structures make identicalcontributions to the entire grating surface. The component can beconfigured so that, for each of at least two of the diffractiongratings, surface areas of the diffraction positive structures and ofthe diffraction negative structures make contributions to the entiregrating surface that differ by at most 20% (e.g., at most 10%, at most5%, at most 4%, at most 3%, at most 2%, at most 1%) from each other.

The component can configured so that, for each of the diffractiongratings, surface areas of the diffraction positive structures and ofthe diffraction negative structures make identical contributions to theentire grating surface. The component can be configured so that, foreach of the diffraction gratings, surface areas of the diffractionpositive structures and of the diffraction negative structures makecontributions to the entire grating surface that differ by at most 20%e.g., at most 10%, at most 5%, at most 4%, at most 3%, at most 2%, atmost 1%) from each other.

In a general aspect, the disclosure provides a lithograph collector thatincludes a component as described herein. The collector mirror can beconfigured to guide: used radiation toward a focal region; and radiationhaving the first wavelength, λ₁, away from the focal region. Thecollector can be an EUV lithography collector.

In a general aspect, the disclosure provides an illumination system thatincludes a collector as described herein, and an illumination opticalunit configured to illuminate an object field.

In a general aspect, the disclosure provides an optical system thatincludes: a collector according as described herein; an illuminationoptical unit configured to illuminate an object field; and a projectionoptical unit configured to image the object field into an image field.

In a general aspect, the disclosure provides an apparatus, thatincludes: a light source; a collector as described herein; anillumination optical unit configured to illuminate an object field; anda projection optical unit configured to image the object field into animage field. The apparatus is a projection exposure apparatus. The lightsource can include an EUV light source. An EUV light source can includea pump light source configured to produce a plasma that generates EUVwavelengths. Optionally: the pump light source is configured to producea prepulse and a main pulse; the prepulse has a prepulse lightwavelength; the main pulse has a main pulse light wavelength; and theprepulse light wavelength differs from the main pulse light wavelength.

In a general aspect, the disclosure provides a method of using aprojection exposure apparatus including an illumination optical unit anda projection optical unit. The method includes: using the illuminationoptical unit to illuminate a reticle in an object field of theprojection optical unit; and using the projection optical unit toproject a structure of the reticle onto a light-sensitive material in animage field of the projection optical unit. The illumination opticalunit includes a collector as described herein.

In a general aspect, the disclosure provides a method that includesmaking a component as described herein. The method can include:disposing a first mask structure between a substrate and an etchingmedium, the first mask substrate including first mask regions and firstgaps between the first mask regions, the first mask regions beingimpenetrable to the etching medium; and using the etching medium to etchthe substrate. The method can further include: exchanging the first maskstructure with a second mask structure different from the first maskstructure, the second mask substrate including second mask regions andsecond gaps between the second mask regions, the second mask regionsbeing impenetrable to the etching medium; and using the etching mediumto further etch the substrate.

In a general aspect, the disclosure provides a method that includesimpinging a wavelength range of light onto a collector so that lighthaving a first wavelength, λ₁, is diffracted away from a focal region ofthe collector. The first wavelength, λ₁, is within the wavelength range.The first wavelength, is in the infrared wavelength range. Thewavelength range includes radiation components including at least threedifferent phases which interfere with each other destructively in atleast one order of diffraction; and The at least one order ofdiffraction is selected from the group consisting of: the zero order ofdiffraction of the first wavelength, λ₁; the + first order ofdiffraction of the first wavelength, λ₁; and the − first order ofdiffraction of the first wavelength, λ₁. The method can further include,simultaneously with impinging the wavelength range of light onto thecollector, impinging EUV light onto the collector so that the EUV lightis diffracted toward the focal region of the collector. Optionally: thewavelength range further includes a second wavelength, λ₂; the methodfurther includes diffracting light having the second wavelength, λ₂,away from the focal region of the collector; the wavelength, λ₂, isdifferent from the first wavelength, λ₁; and the second wavelength, λ₂,is in the infrared wavelength range. The diffraction structures can beconfigured so that the wavelength range further includes radiationcomponents including at least three additional different phases whichinterfere with each other destructively in at least one order ofdiffraction selected from the group consisting of: the zero order ofdiffraction of the first wavelength, λ₂; the + first order ofdiffraction of the first wavelength, λ₂; and the − first order ofdiffraction of the first wavelength, λ₂. (λ₁−λ₂)²/(λ₁+λ₂)² can be <20%(e.g., <15%, <10%, <5%, <4%, <3%, <2%, <1%). The collector can include aperiodic grating structure profile including diffraction structures. Thewavelength range can include radiation components including at leastthree different phases which interfere with one each other destructivelyin the zero order of diffraction of the first wavelength, λ₂. Thewavelength range can include radiation components including at leastthree different phases which interfere with one each other destructivelyin the + first order of diffraction of the first wavelength, λ₂. Themethod wavelength range can include radiation components including atleast three different phases which interfere with one each otherdestructively in the − first order of diffraction of the firstwavelength, λ₂. The wavelength range can include radiation componentsincluding at least three different phases which interfere with one eachother destructively in the zero order of diffraction of the firstwavelength, λ₁. The wavelength range can include radiation componentsincluding at least three different phases which interfere with one eachother destructively in the + first order of diffraction of the firstwavelength, λ₁. The wavelength range can include radiation componentsincluding at least three different phases which interfere with one eachother destructively in the − first order of diffraction of the firstwavelength, λ₁. The method can further include using an illuminationsystem to illuminate a reticle with the EUV light. The method canfurther include using a projection optical unit to project anilluminated structure of the reticle onto a light sensitive material.The collector can include a component as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are explained in greater detailbelow with reference to the drawing. In the drawing:

FIG. 1 schematically shows a projection exposure apparatus for EUVmicrolithography;

FIG. 2 shows details of a light source of the projection exposureapparatus in the environment of an EUV collector for guiding EUV usedlight from a plasma source region to a field facet mirror of anillumination optical unit of the projection exposure apparatus, with theEUV collector being illustrated in a meridional section;

FIG. 3 shows, in a more abstract illustration in comparison with FIG. 3,guidance firstly of EUV used light and secondly of wavelength-differentstray light components in the case of reflection/diffraction at the EUVcollector;

FIG. 4 shows a plan view of a section of a grating surface of an opticalgrating including two diffraction gratings as diffraction structuregroups having mutually perpendicular period running directions andidentical grating periods, wherein structure depths predefining threediffraction structure levels of diffraction structures which are squarein FIG. 4 are illustrated via different types of hatching, wherein theoptical grating constitutes one embodiment of an optical diffractioncomponent for suppressing at least one target wavelength by destructiveinterference;

FIG. 5 shows, in a diagram, a wavelength-dependent reflectivity R of theoptical grating according to FIG. 4 for a calculated ideal case and fora further, calculated, more realistic case and for a reference gratingnot according to the invention, wherein the two diffraction gratings ofthe optical grating are embodied for suppressing two differentwavelengths;

FIG. 6 shows, in a diagram similar to FIG. 5, the relations in the caseof an optical grating according to FIG. 4, wherein the two diffractiongratings have identical structure depths, such that the optical gratingis embodied for suppressing exactly one wavelength;

FIG. 7 shows, in an illustration similar to FIG. 4, a further embodimentof an optical grating including two diffraction gratings as diffractionstructure groups having period running directions which assume an angleof 45° with respect to one another, wherein the optical gratingconstitutes one embodiment of an optical diffraction component forsuppressing at least one target wavelength by destructive interference;

FIG. 8 shows, in an illustration similar to FIG. 4 and FIG. 7, a furtherembodiment of an optical grating including three diffraction gratings asdiffraction structure groups, two of which have period runningdirections which are perpendicular to one another, and a thirddiffraction grating of which has a diagonal period running directionrelative thereto, wherein the optical grating constitutes one embodimentof an optical diffraction component for suppressing at least one targetwavelength by destructive interference;

FIG. 9 shows, in a diagram similar to FIG. 5 and FIG. 6, reflectionrelations in the case of an optical grating according to FIG. 8, inwhich all three diffraction gratings are embodied for suppressing oneand the same wavelength;

FIG. 10 shows, in a diagram similar to FIG. 9, the reflection relationsin the case of an optical grating of the type from FIG. 8, wherein thethree diffraction gratings have different structure depths, such thatthe optical grating is embodied for suppressing different wavelengths;

FIG. 11 shows, in an illustration similar to FIG. 8, a furtherembodiment of an optical grating including three diffraction gratings asdiffraction structure groups having respective period running directionswhich assume in pairs an angle different from zero, wherein the opticalgrating constitutes one embodiment of an optical diffraction componentfor suppressing at least one target wavelength by destructiveinterference;

FIGS. 12 and 13 show, in an illustration similar to FIG. 11, furtherembodiments of optical gratings each including three diffractiongratings as diffraction structure groups having period runningdirections corresponding to those of the embodiment according to FIG.11, wherein the diffraction structures of the embodiments according toFIGS. 12 and 13 are arranged in a manner offset with respect to oneanother and in relation to the embodiment according to FIG. 11 in therespective period running direction, wherein the optical gratingsconstitute further embodiments of optical diffraction components forsuppressing at least one target wavelength by destructive interference;

FIG. 14 shows, in a side view, a first diffraction structure groupbelonging to a further embodiment of an optical diffraction componentfor suppressing at least one target wavelength by destructiveinterference, embodied as a binary grating having a first grating periodand a first structure depth;

FIG. 15 shows, in an illustration similar to FIG. 14, a furtherdiffraction structure group as part of the optical diffractioncomponent, wherein the further diffraction structure group is in turnembodied as a binary grating having a grating period and a structuredepth, wherein a possible overlay error during the production of thisdiffraction structure group is additionally indicated in a dashedmanner;

FIG. 16 shows the optical diffraction component arising as asuperimposition of the two diffraction structure groups according toFIGS. 14 and 15;

FIGS. 17 to 19 show, in illustrations similar to FIGS. 14 to 16, twodiffraction structure groups and the further optical diffractioncomponent arising therefrom as a result of superimposition;

FIGS. 20 to 22 show, in illustrations similar to FIGS. 14 to 16, twodiffraction structure groups and the further optical diffractioncomponent arising therefrom as a result of superimposition;

FIG. 23 shows, in a diagram, a reflectivity of an optical diffractioncomponent of the type of that from FIG. 16, 19 or 22, wherein thestructure height of the respective first diffraction structure group isfixed at a value for suppressing a target wavelength and thereflectivity is plotted as a function of the structure height of theother diffraction structure group;

FIG. 24 shows, once again in a diagram, the reflectivity of the opticaldiffraction component, once again with a fixed structure depth of thefirst diffraction structure group, plotted as a function of a differencebetween the structure depths of the two diffraction structure groups andnormalized to the structure depth of the first diffraction structuregroup;

FIG. 25 shows, in an illustration similar to FIG. 14, a diffractionstructure group, embodied as a binary grating having a grating periodand a structure depth, as part of a further embodiment of an opticaldiffraction component for suppressing at least one target wavelength bydestructive interference, the further embodiment arising as a result ofsuperimposition of three diffraction structure groups;

FIG. 26 shows a further diffraction structure group, once again embodiedas a binary grating, for the embodiment of this variant of the opticaldiffraction component;

FIG. 27 shows a further diffraction structure group, once again embodiedas a binary grating, for the embodiment of this variant of the opticaldiffraction component;

FIG. 28 shows the optical diffraction component, formed as asuperimposition of the three diffraction structure groups according toFIGS. 25 to 27;

FIGS. 29 to 32 show, in an illustration similar to FIGS. 25 to 28, threediffraction structure groups, once again embodied in each case as abinary grating having a grating period and a structure depth, and afurther embodiment of an optical diffraction component for suppressingat least one target wavelength by destructive interference, the furtherembodiment arising therefrom as a result of superimposition;

FIG. 33 shows, in a diagram similar to FIGS. 9 and 10,wavelength-dependent reflection relations in the case of opticaldiffraction components of the type of those according to any of FIG. 8,11 to 13, 28 or 32, wherein the diffraction structure groups havedifferent structure depths, such that the optical grating is embodiedfor suppressing different wavelengths, which however are closer to oneanother in comparison with the variant according to FIG. 10;

FIG. 34 shows, in an illustration similar to FIG. 4, a section of agrating surface of an optical grating including three diffractiongratings as diffraction structure groups, wherein two of the gratingshave parallel period running directions and a third grating has a periodrunning direction perpendicular thereto and wherein the diffractionstructure groups having the same period running direction aresuperimposed in the manner of the embodiment according to FIG. 16, 19 or22, wherein structure depths of diffraction structures that arerectangular in FIG. 34 are illustrated via different types of hatching,as a further embodiment of an optical diffraction component forsuppressing at least one target wavelength by destructive interference;

FIG. 35 shows a further embodiment of an optical diffraction componentfor suppressing at least one target wavelength by destructiveinterference, embodied as a three-level grating, embodied forsuppressing exactly one target wavelength, once again in a schematicside view;

FIG. 36 shows, in an illustration similar to FIG. 35, a furtherembodiment of an optical diffraction component for suppressing at leastone target wavelength by destructive interference, once again fashionedwith three diffraction structure levels which are assignable to twodiffraction structure groups, variables being depicted which aredepicted for the theoretical description of a calculation of anefficiency of the suppression of the at least one target wavelength;

FIG. 37 shows, in an illustration similar to FIGS. 35 and 36, a furtherembodiment of an optical diffraction component for suppressing at leastone target wavelength by destructive interference, embodied with fourdiffraction structure levels which are assignable to a correspondingplurality of diffraction structure groups;

FIGS. 38 and 39 show, in illustrations similar to FIG. 37, two furtherembodiments of optical diffraction components for suppressing at leastone target wavelength by destructive interference, embodied once againwith four diffraction structure levels;

FIG. 40 shows, in a diagram, a wavelength-dependent reflectivity of anoptical diffraction component including two diffraction structure groupsof the type for example of the embodiments according to FIGS. 4, 7, 16,19, 22, 35, 36, wherein the two diffraction structure groups areembodied with structure depths for suppressing two DUV wavelengths;

FIG. 41 shows, in an illustration similar to FIG. 40, awavelength-dependent reflectivity for an optical diffraction componentincluding a total of five diffraction structure levels, to which fourdiffraction structure groups having different structure depths areassignable, wherein two target wavelengths in the IR range above 10 μmand two target wavelengths in the DUV range comparable to the targetwavelengths according to FIG. 40 are suppressed;

FIG. 42 shows a magnified detail from FIG. 41 in the DUV range ofbetween 0.1 μm and 0.4 μm;

FIG. 43 shows, once again in a diagram, a wavelength-dependentreflectivity of between 10.0 μm and 11.0 μm for various opticaldiffraction components having a different sidewall steepness toleranceof the diffraction structure groups;

FIG. 44 shows the optical diffraction component according to FIG. 16together with two lithographic mask structures, which can be used in theproduction of the optical diffraction component for predefining boundaryregions between adjacent surface sections of binary structures of theoptical diffraction component, the binary structures being superimposedon one another;

FIG. 45 shows, in an illustration similar to FIG. 44, the opticaldiffraction component according to FIG. 19 together with twolithographic mask structures, which can be used in the production of theoptical diffraction component for predefining once again the boundaryregions between the surface sections of the diffraction structuregroups;

FIG. 46 shows a further embodiment of an optical diffraction componentfor suppressing at least one target wavelength by destructiveinterference including a periodic grating structure profile includingdiffraction structures having three diffraction structure levelsarranged in such a way that the target wavelength is suppressed bydestructive interference;

FIG. 47 shows the optical diffraction component according to FIG. 46,wherein the three diffraction structure levels have a height or leveldifference with respect to one another which leads to perfectdestructive interference of the target wavelength in the zero order ofdiffraction;

FIG. 48 shows, in an illustration similar to FIG. 47, a variant of theoptical diffraction component according to FIG. 46, wherein firstly apositive diffraction structure level and secondly a negative diffractionstructure level are embodied with a height difference that is somewhattoo large relative to a neutral diffraction structure level, forillustrating a diffraction compensation effect that arises in the caseof such a height error;

FIG. 49 shows, in an illustration similar to FIG. 46, a furtherembodiment of an optical diffraction component including threediffraction structure levels in a different sequence in comparison withthe embodiment according to FIG. 46;

FIG. 50 shows a further embodiment of an optical diffraction component,wherein substantially one grating period is illustrated and wherein aperiodic grating structure profile of the optical diffraction componentincludes diffraction structures having four diffraction structurelevels;

FIG. 51 shows, in an illustration similar to FIG. 50, a furtherembodiment of an optical diffraction component including fivediffraction structure levels within one grating period;

FIG. 52 shows, in a diagram similar to FIG. 5, a wavelength-dependentreflectivity R of an optical diffraction component in the form of anoptical grating, fashioned in the manner of FIGS. 19, 36, 45 and 46 withthree diffraction structure levels which are assignable to twodiffraction structure groups, wherein there is a structure depthdifference between the diffraction structure levels in each case of λ4,wherein λ is the target wavelength to be suppressed in each case;

FIG. 53 shows, in an illustration similar to FIGS. 44 and 45, theoptical diffraction component of the type from FIGS. 19, 36, 45 and 46together with a further embodiment of two lithographic mask structures,which can be used in the production of the optical diffraction componentfor predefining once again the boundary regions between the surfacesections or the diffraction structure levels of the diffractionstructure groups;

FIG. 54 shows, in an illustration similar to FIGS. 44 and 45, theoptical diffraction component of the type from FIGS. 19, 36, 45 and 46together with a further embodiment of two lithographic mask structures,which can be used in the production of the optical diffraction componentfor predefining once again the boundary regions between the surfacesections or the diffraction structure levels of the diffractionstructure groups;

FIG. 55 shows, in an illustration similar to FIGS. 44 and 45, a furtherembodiment of an optical diffraction component of the type from FIGS.19, 36, 45 and 46 together with a further embodiment of two lithographicmask structures, which can be used in the production of the opticaldiffraction component for predefining once again the boundary regionsbetween the surface sections or the diffraction structure levels of thediffraction structure groups; and

FIG. 56 shows, in an illustration similar to FIGS. 44 and 45, a furtherembodiment of an optical diffraction component of the type from FIGS.19, 36, 45 and 46 together with a further embodiment of two lithographicmask structures, which can be used in the production of the opticaldiffraction component for predefining once again the boundary regionsbetween the surface sections or the diffraction structure levels of thediffraction structure groups.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A projection exposure apparatus 1 for microlithography includes a lightsource 2 for illumination light or imaging light 3, which will beexplained in yet more detail below. The light source 2 is an EUV lightsource, which produces light in a wavelength range of, for example,between 5 nm and 30 nm, in particular between 5 nm and 15 nm. Theillumination light or imaging light 3 is also referred to as EUV usedlight below.

In particular, the light source 2 can be a light source with awavelength of 13.5 nm or a light source with a wavelength of 6.9 nm.Other EUV wavelengths or else wavelengths in the DUV range of between150 nm and 250 nm, for example of 193 nm, are also possible. A beam pathof the illumination light 3 is illustrated extremely schematically inFIG. 1.

An illumination optical unit 6 serves to guide the illumination light 3from the light source 2 to an object field 4 in an object plane 5. Theillumination optical unit includes a field facet mirror FF illustratedhighly schematically in FIG. 1 and a pupil facet mirror PF disposeddownstream in the beam path of the illumination light 3 and likewiseillustrated highly very schematically. A field-forming mirror 6 b forgrazing incidence (GI mirror; grazing incidence mirror) is arranged inthe beam path of the illumination light 3 between the pupil facet mirrorPF, which is arranged in a pupil plane 6 a of the illumination opticalunit, and the object field 4. Such a GI mirror 6 b is not mandatory.

Pupil facets (not illustrated in any more detail) of the pupil facetmirror PF are part of a transfer optical unit, which transfer, and inparticular image, field facets (likewise not illustrated) of the fieldfacet mirror FF into the object field 4 in a manner being superimposedon one another. An embodiment known from the prior art can be used forthe field facet mirror FF on the one hand and the pupil facet mirror PFon the other hand. By way of example, such an illumination optical unitis known from DE 10 2009 045 096 A1.

Using a projection optical unit or imaging optical unit 7, the objectfield 4 is imaged into an image field 8 in an image plane 9 with apredetermined reduction scale. Projection optical units which may beused to this end are known from e.g. DE 10 2012 202 675 A1.

In order to facilitate the description of the projection exposureapparatus 1 and the various embodiments of the projection optical unit7, a Cartesian xyz-coordinate system is indicated in the drawing, fromwhich system the respective positional relationship of the componentsillustrated in the figures is evident. In FIG. 1, the x-direction runsperpendicular to the plane of the drawing into the latter. They-direction extends towards the left in FIG. 1 and the z-direction runsupwards in FIG. 1. The object plane 5 runs parallel to the xy-plane.

The object field 4 and the image field 8 are rectangular. Alternatively,it is also possible for the object field 4 and the image field 8 to havea bent or curved embodiment, that is to say, in particular, a partialring shape. The object field 4 and the image field 8 have an x/y-aspectratio of greater than 1. Therefore, the object field 4 has a longerobject field dimension in the x-direction and a shorter object fielddimension in the y-direction. These object field dimensions extend alongthe field coordinates x and y.

One of the exemplary embodiments known from the prior art can be usedfor the projection optical unit 7. What is imaged in this case is aportion of a reflection mask 10, also referred to as reticle, coincidingwith the object field 4. The reticle 10 is carried by a reticle holder10 a. The reticle holder 10 a is displaced by a reticle displacementdrive 10 b.

The imaging by way of the projection optical unit 7 is implemented onthe surface of a substrate 11 in the form of a wafer, which is carriedby a substrate holder 12. The substrate holder 12 is displaced by awafer or substrate displacement drive 12 a.

FIG. 1 schematically illustrates, between the reticle 10 and theprojection optical unit 7, a ray beam 13 of the illumination light 3that enters into the projection optical unit and, between the projectionoptical unit 7 and the substrate 11, a ray beam 14 of the illuminationlight 3 that emerges from the projection optical unit 7. An imagefield-side numerical aperture (NA) of the projection optical unit 7 isnot reproduced to scale in FIG. 1.

The projection exposure apparatus 1 is of the scanner type. Both thereticle 10 and the substrate 11 are scanned in the y-direction duringthe operation of the projection exposure apparatus 1. A stepper type ofthe projection exposure apparatus 1, in which a stepwise displacement ofthe reticle 10 and the substrate 11 in the y-direction is implementedbetween individual exposures of the substrate 11, is also possible.These displacements are effected synchronously with one another by anappropriate actuation of the displacement drives 10 b and 12 a.

FIG. 2 shows details of the light source 2.

The light source 2 is an LPP (laser produced plasma) source. For thepurposes of producing plasma, tin droplets 15 are generated as acontinuous droplet sequence by a tin droplet generator 16. A trajectoryof the tin droplets 15 extends transversely to a principal ray direction17 of the EUV used light 3. Here, the tin droplets 15 drop freelybetween the tin droplet generator 16 and a tin capturing device 18, withthe droplets passing through a plasma source region 19. The EUV usedlight 3 is emitted by the plasma source region 19. When the tin droplet15 arrives in the plasma source region 19, it is impinged upon there bypump light 20 from a pump light source 21. The pump light source 21 canbe an infrared laser source in the form of e.g. a CO₂ laser. Some otherIR laser source is also possible, in particular a solid-state laser, forexample an Nd:YAG laser. The pump light source 21 can include a lightsource unit for producing a light prepulse and a light source unit forproducing a main light pulse. The light prepulse, on the one hand, andthe main light pulse, on the other hand, can have different lightwavelengths.

The pump light 20 is transferred into the plasma source region 19 by wayof a mirror 22, which can be a mirror that is tiltable in a controlledfashion, and by way of a focusing lens element 23. A plasma emitting theEUV used light 3 is produced by the pump light impingement from the tindroplet 15 arriving in the plasma source region 19. A beam path of theEUV used light 3 is illustrated in FIG. 2 between the plasma sourceregion 19 and the field facet mirror FF, to the extent that the EUV usedlight is reflected by a collector mirror 24, which is also referred toas EUV collector 24 below. The EUV collector 24 includes a centralpassage opening 25 for the pump light 20 focussed towards the plasmasource region 19 by way of the focusing lens element 23. The collector24 is embodied as an ellipsoid mirror and transfers the EUV used light 3emitted by the plasma source region 19, which is arranged at oneellipsoid focus, to an intermediate focus 26 of the EUV used light 3,which is arranged at the other ellipsoid focus of the collector 24.

The field facet mirror FF is disposed downstream of the intermediatefocus 26 in the beam path of the EUV used light 3, in the region of afar field of the EUV used light 3.

The EUV collector 24 and further components of the light source 2, whichmay be the tin droplet generator 16, the tin capturing device 18 and thefocusing lens element 23, are arranged in a vacuum housing 27. Thevacuum housing 27 has a passage opening 28 in the region of theintermediate focus 26. In the region of an entrance of the pump light 20into the vacuum housing 27, the latter includes a pump light entrancewindow 29 for the light prepulse and for the main light pulse.

FIG. 3 shows highly abstractly guidance firstly of EUV used light, thatis to say the illumination light 3, and secondly of stray light 30, inparticular of radiation of longer wavelength, for example IR radiationhaving the wavelengths of the light prepulse and/or of the main lightpulse, between the plasma source region 19 of the light source 2 and anintermediate focal plane 26 a, in which the intermediate focus 26 isarranged. At the same time FIG. 3 shows a variant the manner in which ofthe pump light 20 is guided to the plasma source region 19, that is tosay guidance which does not involve a passage opening of the type of thepassage opening 25 in the EUV collector 24. In the case of FIG. 3, thepump light is laterally guided to the plasma source region 19. However,other approaches may be used with or without a passage opening 25 in theEUV collector 24.

Optionally, guidance of the pump light 20 to the source region 19 mayinclude multiple passage openings in the collector 24 and/or may involveguidance of the pump light 20 to the source region 19 from multipledifferent directions without having the pump light 20 pass through apassage opening in the collector 24. Referring again to FIG. 3, both theused light 3 and the stray light 30 emanate from the plasma sourceregion 19. Both the used light 3 and the stray light 30 are incident onsurface sections 31, 32 of an entire impingement surface 33 of the EUVcollector 24. The surface sections 31, 32 are sections of a gratingsurface—likewise designated by 33 in the drawing—of the EUV collector24. An optical grating for diffractively dumping the stray lightradiation 30 is arranged on the grating surface. Embodiments of theoptical grating are described below. The grating surface can be arrangedexclusively at the location of the surface sections 31, 32 on which thestray light 30 impinges, or can alternatively also cover larger sectionsof the impingement surface 33, and cover the entire impingement surface33 in a further variant. In general, the grating surface can have anyconfiguration that may be effective in diffractively directing undesiredlight (e.g., the stray light 30) from the beam path of the used light 3.

FIG. 4 shows an embodiment of an optical grating 34 on a section of thegrating surface 33. The optical grating 34 constitutes an opticaldiffraction component for suppressing at least one target wavelength bydestructive interference.

The grating surface of the optical grating 34 can be embodied as planeor else curved, e.g. concave like the impingement surface 33 in the caseof the collector mirror 24 according to FIGS. 2 and 3, or else convex.Combinations of shapes of the optical grating 34 are also possible. Asan example, one or more different regions of the optical grating 34 maybe concave, while one or more different regions of the optical grating34 may be convex, and/or while one or more different regions of theoptical grating 34 may be planar.

The optical grating 34 has, as diffraction structure groups, twodiffraction gratings 35, 36 arranged on the grating surface 33. Thediffraction grating 35 is also referred to hereinafter as firstdiffraction grating. The diffraction grating 36 is also referred tohereinafter as second diffraction grating.

In the case of the diffraction grating 35, diffraction positivestructures 37 and diffraction negative structures 38 run alternately ineach case horizontally in FIG. 4. A period running direction 39 of thisfirst diffraction grating 35 runs perpendicularly. For this horizontalcourse of the diffraction structures 37, 38, the period runningdirection 39 thus runs vertically in FIG. 4.

In FIG. 4, the second diffraction grating 36 has vertically runningdiffraction positive structures 40 and diffraction negative structures41 respectively alternating therewith. A period running direction 42 ofthe second diffraction grating 36 once again runs perpendicularly to thediffraction structures 40, 41, that is to say horizontally, in FIG. 4.

The diffraction structures 37, 38 and 40, 41 of the two diffractiongratings 35, 36 of the optical grating 34 are realized by fourdiffraction structure types or diffraction structure levels, whichdiffer in their structure depth and are illustrated in FIG. 4 bydifferent types of hatching and by numerals 1, 2, 3, 4 applied to therespective diffraction structure. The diffraction structure type “1” hasthe structure depth 0. The diffraction structure type “2” has thestructure depth “dv”. That surface section of the grating surface whichis occupied by the respective diffraction structure type “2” is thus ata location deeper than the diffraction structure type “1” by thestructure depth dv perpendicularly to the plane of the drawing in FIG.4.

The respective structure depth can be assigned a depth value relative toa reference plane, wherein as a general rule the reference plane chosenis the one for which no material is removed (structure depth=0).

The respective areas of the diffraction structure types “1” to “4” aresquare in each case. Other boundary shapes of the diffraction structuretypes which result in complete coverage of the grating surface are alsopossible. Such boundary shapes include, for example, those havingstraight sides, such as, for example, rectangular, trapezoidal,triangular, scalene, pentagonal, hexagonal, octagonal, and/orparallelogram, generally so long as complete coverage of the gratingsurface is achieved via the use such boundary shapes.

The diffraction structure type “3” has a structure depth dh, once againmeasured relative to the diffraction structure type “1” perpendicularlyto the plane of the drawing in FIG. 4. The diffraction structure type“4” has a correspondingly measured structure depth dv+dh.

In the case of the optical grating 34, the four diffraction structuretypes “1” to “4” are respectively arranged in a 2×2 array, wherein thediffraction structure type “1” is arranged at the top left, thediffraction structure type “2” is arranged at the top right, thediffraction structure type “3” is arranged at the bottom left and thediffraction structure type “4” is arranged at the bottom right. These2×2 arrays of such groups of the 4 diffraction structure types in eachcase are in turn arranged in a superstructure in the form of a 3×3 arrayin the embodiment according to FIG. 4. Generally, the optical grating 34on the grating surface 33 can, of course, be extended in any desired wayhorizontally and vertically by attachments of further corresponding 2×2arrays of the four diffraction structure types “1” to “4”.

Diffraction positive structures 37 and diffraction negative structures38 situated at a position deeper by the structure depth dh in comparisontherewith thus succeed one another in the period running direction 39 ofthe first diffraction grating 35. In the case of the second diffractiongrating 36, one of the diffraction positive structures 40 isrespectively followed, in the period running direction 42, by adiffraction negative structure 41 situated at a position deeper by thestructure depth dv. Two diffraction gratings 35, 36 being superimposedon one another and having respective structure depths dh and dv are thusrealized in the optical grating 34.

In the case of the embodiment according to FIG. 4, the structure depthis the height difference between the respective diffraction positivestructures and the associated diffraction negative structures. Moregenerally, the structure depth can be understood as an optical pathdifference between the diffraction positive structures and theassociated diffraction negative structures.

On the diffraction positive structures 37, 40 and the diffractionnegative structures 38, 41, over the whole area it is possible to applya highly reflective coating on the optical grating 34, and optionallyalso an auxiliary layer.

The auxiliary layer, which is arranged below the highly reflectivecoating, can be a layer that increases a lifetime of the optical grating34. Alternatively or additionally, an auxiliary layer can also beapplied on the highly reflective coating in order to protect the latteragainst damage.

The highly reflective coating can be a multilayer, such as is known forthe highly effective reflection of, in particular, radiation having EUVwavelengths.

The diffraction gratings 35, 36 of the optical grating 34 are embodiedin each case as a binary grating. Here the surface area of thediffraction positive structures is equal to the surface area of thediffraction negative structures.

A grating period of the diffraction grating 35 can be in the range ofbetween 0.5 mm and 5 mm (e.g., from 0.5 mm to 4.5 mm, from 0.5 mm to 4mm, from 0.5 mm to 3.5 mm, from 0.5 mm to 3 mm, from 0.5 mm to 2.5 mm,from 0.5 mm to 2 mm, from 0.5 mm to 1.5 mm, from 0.5 mm to 1 mm, from 1mm to 5 mm, from 1.5 mm to 5 mm, from 2 mm to 5 mm, from 2.5 mm to 5 mm,from 3 mm to 5 mm, from 3.5 mm to 5 mm, from 4 mm to 5 mm, from 4.5 mmto 5, 2 mm). A grating period of the diffraction grating 36 can be inthe range of between 0.5 mm and 5 mm (e.g., from 0.5 mm to 4.5 mm, from0.5 mm to 4 mm, from 0.5 mm to 3.5 mm, from 0.5 mm to 3 mm, from 0.5 mmto 2.5 mm, from 0.5 mm to 2 mm, from 0.5 mm to 1.5 mm, from 0.5 mm to 1mm, from 1 mm to 5 mm, from 1.5 mm to 5 mm, from 2 mm to 5 mm, from 2.5mm to 5 mm, from 3 mm to 5 mm, from 3.5 mm to 5 mm, from 4 mm to 5 mm,from 4.5 mm to 5, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4mm, 4.5 mm, 5 mm).

Such a grating period is designated by P for the second diffractiongrating 36 in FIG. 4. A structure sidewall of the respective diffractionstructures 37, 38, 40, 41 can have an extent in the range of between 1μm and 10 μm (e.g., from 1 μm to 9 μm, from 1 μm to 8 μm, from 1 μm to 7μm, from 1 μm to 6 μm, from 1 μm to 5 μm, from 1 μm to 4 μm, from 1 μmto 3 μm, from 1 μm to 2 μm, from 2 μm to 10 μm, from 3 μm to 10 μm, from4 μm to 10 μm, from 5 μm to 10 μm, from 6 μm to 10 μm, from 7 μm to 10μm, from 8 μm to 10 μm, from 9 μm to 10 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm), perpendicularly to the extension ofthe respective diffraction structure, that is to say measured in therespective period running direction 39 to 42. Such a sidewall extent orsidewall extension is indicated at F with a greatly exaggerated size forthe second diffraction grating 36 in FIG. 4.

FIG. 5 shows, in a diagram, the result of a calculation of awavelength-dependent reflectivity of the optical grating 34 for thedesign parameters dv=2.65 μm and dh=2.55 μm. A reflectivity of theoptical grating 34 is plotted at 43, the reflectivity resulting as theresult of a calculation in which it is additionally assumed that thesidewall extension F is 0, that is to say the result in the case of anoptical grating 34 having ideally steep sidewalls between thediffraction structures. In the case of the suppression designwavelengths 10.2 μm and 10.6 μm for corresponding stray lightwavelengths, which are referred to as target wavelengths, the result isa reflectivity suppression of the optical grating 34 in the ideal caseof the reflectivity curve 43 of better than 10⁻⁸. These two wavelengthscorrespond to the wavelengths of the prepulse and of the main pulse ofthe pump light source 21.

For the two target wavelengths 10.2 μm (λ₁) and 10.6 μm (λ₂) it holdstrue that:(λ₁−λ₂)²/(λ₁+λ₂)²=3.77·10⁻⁴

For this normalized target wavelength ratio it thus holds true that:(λ₁−λ₂)²/(λ₁+λ₂)²<10%

This normalized target wavelength ratio can also be less than 20%.

A reflectivity curve R (λ) taking account of specific tolerances as faras firstly the accuracy of the production of the structure depths dv anddh and also the sidewall steepness are concerned is plotted at 44 inFIG. 5. In the case of the target wavelengths 10.2 μm and 10.6 μm, theresult is a reflectivity suppression that is better than 10⁻⁶.

A reference reflectivity curve 45 is also entered in FIG. 5 forcomparison purposes, the reference reflectivity curve representing thesuppression result for an optical reference grating including exactlyone diffraction grating, that is to say e.g. either the diffractiongrating 35 having the horizontal diffraction structures or thediffraction grating 36 having the vertical diffraction structures. Thesame tolerances for the structure depth production and for the sidewallsteepness as in the case of the reflectivity curve 44 are taken intoaccount here. It is evident that, despite the same tolerances, thereference reflectivity curve 45 exhibits a significantly lower optimumreflectivity suppression in the region of 10⁻⁴. Since the referencegrating for which the reference reflectivity curve 45 was calculatedincludes moreover just one diffraction grating, only exactly onewavelength is also suppressed here, namely 10.6 μm.

The two diffraction gratings 35, 36 have a ratio between a gratingperiod (2 mm) and a structure depth (in the region of 2.6 μm) which issignificantly greater than 10 and is actually greater than 500 and is inthe region of 1000. Exemplary ratios include 100, 150, 200, 250, 300,350, 400, 450, 500, 550, 600, 650 700, 750, 800, 850, 900, 950 and 1000.

On account of the embodiment of the two diffraction gratings 35, 36 asbinary gratings, a surface area ratio of the surface areas of thediffraction positive structures 37, 40 to surface areas of thediffraction negative structures 38, 41 is 1. Depending on the embodimentof the optical grating 34, the surface area ratio can also deviate from1 and can be in the range of between 0.9 and 1.1 (e.g., 0.9, 0.95, 1,1.05, 1.1).

The two diffraction gratings 35, 36 have the same grating period p, andso a period ratio of the two grating periods is 1 (e.g., 0.9, 0.95, 1,1.05, 1.1). Depending on the embodiment of the optical grating 34, theperiod ratio can be in the range of between 0.9 and 1.1 (e.g., 0.9,0.95, 1, 1.05, 1.1). The differences between the two grating periods canalso be significantly greater, such that for example a period ratio of1:2 or of 1:5 results.

The optical grating 34 constitutes an optical diffraction component forsuppressing at least one target wavelength λ₁, λ₂ by destructiveinterference including at least three diffraction structure levelscorresponding to the diffraction structure types 1 to 4. The diffractionstructure levels N₁ to N₄ predefine different structure depths d_(i)relative to a reference plane. The diffraction structure levels N₁ to N₄can be assigned to the two diffraction gratings, that is to say twodiffraction structure groups 35, 36, which in turn serve for suppressingrespectively one of the two target wavelengths λ₁, λ₂. The first of thediffraction structure groups, that is to say the diffraction grating 35,serves for suppressing the first target wavelength λ₁ in the zero orderof diffraction and the second of the diffraction structure groups, thatis to say the diffraction grating 36, serves for suppressing the secondtarget wavelength λ₂ in the zero order of diffraction.

The topography of the diffraction structure levels N₁ to N₄ can bedescribed as a superimposition of the two binary diffraction structuregroups 35 and 36. Each of these two binary diffraction structure groupshas first surface sections having a first structure depth and secondsurface sections having a second structure depth, which alternate withthe first surface sections along a running direction of the respectivediffraction structure group 35, 36. Boundary regions between theseadjacent surface sections of each of the binary diffraction structuregroups have a linear course. Depending on the embodiment of the opticalgrating 34, the linear course corresponds to the rows and columns of thediffraction structure type arrangement resembling a checkerboard in FIG.4. First boundary regions of the first of the two binary diffractionstructure groups 35, that is to say the row lines in FIG. 4, and secondboundary regions of the second of the two binary diffraction structuregroups 36, that is to say the column lines in FIG. 4, are superimposedon one another at most along sections of their linear course, namely inthe region of the points of intersection between the row and columnlines in the illustration according to FIG. 4.

The diffraction grating 35 has a first grating period having a firststructure depth, measured as optical path difference between firstdiffraction positive structures 37 and first diffraction negativestructures 38 perpendicular to a surface section of the grating surface33 that respectively surrounds these first structures. The seconddiffraction grating 36 has a second grating period and a secondstructure depth, which is in turn embodied as optical path differencebetween the second diffraction positive structures 40 and seconddiffraction negative structures 41 perpendicular to a surface section ofthe grating surface 33 that respectively surrounds these secondstructures. The two period running directions along which the twograting periods of these gratings 35, 36 run are perpendicular to oneanother, that is to say do not run parallel to one another.

On account of the optical grating 34, the collector mirror of the EUVcollector 24 is embodied such that it guides the EUV radiation 3 throughtowards the focal region 26, wherein the grating 34 is embodied as anoptical diffraction component such that the optical diffractioncomponent guides the radiation 30 of the at least one target wavelength,that is to say the stray light, away from the focal region 26.

FIG. 6 shows, in an illustration similar to FIG. 5, reflectivityrelations in a variant of the optical grating 34 in which the structuredepths dv, dh are equal in magnitude and have an absolute value of 2.65μm. Both diffraction gratings 35, 36 then contribute to suppressing thestray light wavelength of 10.6 μm. Accordingly, once again bettersuppression relations arise in the case of the ideal reflectivity curve43 and in the case of the reflectivity curve 44 calculated with thedesign tolerances.

FIG. 7 shows, in an illustration similar to FIG. 4, a variant of theoptical grating which can be used instead of the optical grating 34according to FIG. 4 as an optical diffraction component for suppressingat least one target wavelength by destructive interference. Componentsand functions corresponding to those which have already been explainedabove with reference to FIG. 4 bear the same reference signs and willnot be discussed in detail again.

The optical grating 46 according to FIG. 7 differs from that from FIG. 4preliminary in that a period running direction 39 of the firstdiffraction grating 35 does not run vertically, but rather at an angleof 45° with respect to the horizontal. Accordingly, the diffractionstructure types “1” to “4” arise with rhombic areas.

FIG. 8 shows a further embodiment of an optical grating 47 which can beused as an alternative or in addition to the above-described opticalgratings as an optical diffraction component for suppressing at leastone target wavelength by destructive interference. Components andfunctions corresponding to those which have already been explained abovewith reference to FIG. 1 to FIG. 7, and particularly with reference toFIG. 4 to FIG. 7, bear the same reference signs and will not bediscussed in detail again.

The optical grating 47 has a total of three diffraction gratings asdiffraction structure groups, wherein two of these three diffractiongratings correspond to the diffraction gratings 35 and 36 of theembodiment according to FIG. 4. In FIG. 8, a grating period of thediffraction grating 35 is illustrated at ph, and a grating period of thediffraction grating 36 at pv.

A third diffraction grating 48 of the optical grating 47 has diffractionpositive structures 49 and diffractive negative structures 50 runningdiagonally with respect to the diffraction structures 37, 38 and 40, 41of the first two diffraction gratings 35, 36. In comparison with thediffraction positive structures 49, the diffraction negative structures50 have a structure depth illustrated by dd in FIG. 8.

An overall height profile over the entire illustrated section of thegrating surface of the optical grating 47 can be understood as ajuxtaposition of basic sections in the form of 2×4 arrays, which arepredefined by the boundaries of the horizontally running diffractionstructures 37, 38 of the diffraction grating 35 and the verticallyrunning diffraction structures 40, 41 of the diffraction grating 36.Diffraction structure types or diffraction structure levels on this 2×4array are designated by “000”, “001”, “010”, “011”, “100”, “101”, “110”and “111” on the 2×4 array arranged at the top left in FIG. 8.

The table below indicates the structure depths of these diffractionstructure types and also the surface area proportions thereof in unitsof the grating periods ph, pv:

TABLE 1 Diffraction Surface area structure type Structure depthproportion 000 0 (ph + pv)/4 001 dd (ph + pv)/4 010 dv (ph + pv)/4 011dv + dd (ph + pv)/4 100 dh (ph + pv)/4 101 dh + dd (ph + pv)/4 110 dh +dv (ph + pv)/4 111 dh + dv + dd (ph + pv)/4

All diffraction structure types “000” to “111” have the same surfacearea proportion (ph+pv)/4 of the total surface area of the opticalgrating 47. This ensures that all three diffraction gratings 35, 36 and48 of the optical grating 47 constitute binary gratings and thediffraction positive structures 37, 40, 49 thereof have a surface arearatio of 1 in each case with respect to the diffraction negativestructures 38, 41, 50 thereof.

A period running direction 51 of the third diffraction grating 48 runsalong a grating period pd at an angle of approximately 23° with respectto the period running direction 39 of the diffraction grating 35. Thisperiod running direction 51 is chosen together with an offset of anarrangement of the diffraction structures 49, 50 of the thirddiffraction grating 48 such that boundaries between the diffractionstructures 49, 50 of the third diffraction grating 48 run alongdiagonals of two structure zones lying horizontally next to one another,which are formed by the diffraction structures 37, 38, firstly, and 40,41, secondly, that intersect one another. An offset variation of thisarrangement of the diffraction structures 49, 50 along the periodrunning direction 51 of the third diffraction grating 48 is possible, asindicated by a double-headed arrow 52 in FIG. 8.

The grating period pd of the third diffraction grating 48 is of theorder of magnitude of the grating periods ph, pv and is approximately1.7 mm in the case of the optical grating 47.

FIG. 9 shows, in an illustration similar to FIGS. 5 and 6, dataconcerning the wavelength-dependent reflectivity R for the case wherethe structure depths dh, dv and dd are each equal in magnitude and havethe value 2.65 μm in the example described.

A reflectivity for the ideal case of preferably steep sidewalls(sidewall extension 0) for the diffraction gratings 35, 36 and 48 isillustrated at 53 in FIG. 9. A reflectivity suppression of a targetwavelength of 10.6 μm is better than 10⁻¹⁰ by orders of magnitude. 54illustrates the calculated result of the wavelength-dependentreflectivity, wherein once again realistic tolerances would be assumedfor the structure depths of the diffraction structures 37, 38, 40, 41,49, 50 and for the sidewall extensions. The result for the opticalgrating 47 including the three diffraction gratings 35, 36, 48 is areflectivity suppression which although lower than in the ideal case, isstill distinctly better than 10⁻¹⁰.

As reference values, FIG. 9 also depicts the reflectivity curves 44 and45 in accordance with FIG. 6 firstly for the optical grating 34including the two diffraction gratings 35, 36 and for the conventionaloptical grating including exactly one diffraction grating.

FIG. 10 shows, once again in a wavelength-dependent diagram, thereflectivity relations of an embodiment of the optical grating 47 havingthe following structure depths:

dh=2.55 μm, dv=2.65 μm and dd=0.26 μm.

The structure depth dd of the diagonally running diffraction structures49, 50 is thus smaller than the structure depths of the diffractionstructures 37, 38, 40, 41 of the diffraction gratings 35, 36 of theoptical grating 47 by approximately a factor of 10.

The reflectivity once again for an ideal design of such an opticalgrating 47 with a sidewall extension 0 is illustrated at 55 in FIG. 10.For the two suppression wavelengths at approximately 10.2 μm (λ₁) andapproximately 10.59 μm (λ₂) and also at a further wavelength in theregion of 1.05 μm, a reflectivity suppression of the optical grating isin each case in the region of 10⁻⁸ or better.

For the two IR wavelengths λ₂ that are suppressed as target wavelengthsby the optical grating 47, the explanation given above in associationwith the optical grating 34 according to FIG. 4 holds true in turn forthe normalized difference in the target wavelengths.

A reflectivity curve having predefined tolerances for the structuredepths, firstly, and the sidewall extension, secondly, is in turncalculated at 56 in FIG. 10.

In the case of the optical grating 47, a diffraction grating 48 having afurther grating period pd and a further structure depth dd is thuspresent, the structure depth being measured as optical path differencebetween the diffraction positive structures 49 and the diffractionnegative structures 50 perpendicular to a surface section of the gratingsurface 33 that respectively surrounds these two structures 49, 50. Theratio pd/dd between the grating period pd of the diffraction grating 48and the structure depth dd of the diffraction grating 48 is greater than10. Alternatively or additionally, the period ratio ph/pd can be in therange of between 0.9 and 1.1 (e.g., 0.9, 0.95, 1, 1.05, 1.1).Alternatively or additionally, the first grating period ph can run alongthe first period running direction 39 of the first diffraction grating35 and the further grating period pd can run along the further periodrunning direction 51 of the further diffraction grating 48 and the twoperiod running directions 39, 51 run parallel to one another.

The surface areas of the diffraction positive structures 37, 40, 49 andof the diffraction negative structures 38, 41, 50 of the variousdiffraction structure groups 35, 46, 48 make identical contributions tothe entire grating surface 33.

A further embodiment of an optical grating 57, once again includingthree diffraction gratings 35, 36, 48, is described below with referenceto FIG. 11. Components and functions corresponding to those which havealready been explained above with reference to FIGS. 1 to 10, andparticularly with reference to FIG. 8, bear the same reference signs andwill not be discussed in detail again.

The optical grating 57 differs from the optical grating 47 primarily inthe orientation of the three period running directions 39, 42 and 51 ofthe three diffraction gratings 35, 36 and 48 placed one above another.The period running direction 39 of the first diffraction grating 35 runsat an angle of approximately 23° with respect to the vertical in FIG.11.

The period running direction 42 of the second diffraction grating 36runs horizontally.

The period running direction 51 of the third diffraction grating 48 runsin turn at an angle of approximately 23° with respect to the vertical,wherein the two period running directions 39 and 51 firstly of the firstdiffraction grating 35 and secondly of the third diffraction grating 48assume an angle of approximately 46° with respect to one another.

FIG. 11 highlights a rhombic basic section of the optical grating 57corresponding to the 2×4 array of the optical grating 47 once again withdiffraction structure types “000” to “111”. An assignment of thestructure depths and also of the surface area proportions in the case ofthese diffraction structure types “000” to “111” of the optical grating57 is just like as indicated above in Table 1 concerning FIG. 8.

In the case of the optical grating 57, an offset of structure boundariesof the third diffraction grating 48 along the period running direction51 is such that structure boundaries between the diffraction structures37, 38 of the first diffraction grating 35, between the diffractionstructures 40, 41 of the second diffraction grating 36 and between thediffraction structures 49, 50 of the third diffraction grating 48intersect in each case at a point P in the centre of the basic sectionillustrated in FIG. 11.

In the case of the optical grating 57, the grating period ph isapproximately 3.25 mm, the grating period pv is 2 mm and the gratingperiod pd is of exactly the same magnitude as the grating period ph.

FIGS. 12 and 13 show further embodiments of optical gratings 58, 59,which differ from the optical grating 57 merely in the size of theoffset of the arrangement of the structure boundaries between thediffraction structures 49, 50 along the period running direction 51. Inthe case of the optical grating 58 according to FIG. 12, the offset issuch that the structure boundaries of the various diffraction gratings35, 36, 48 do not intersect at a point in the respective basic section.In the case of the optical grating 59 according to FIG. 13, the offsetis such that the structure boundaries of the three diffraction gratings35, 36, 48 intersect at different positions within the respective basicsection in comparison with the embodiment according to FIG. 11, thusresulting in turn in a different distribution of the diffractionstructure types “000” to “111”.

The assignment of the structure depths and the surface area proportionsof the diffraction structure types “000” to “111” indicated within thehighlighted unit cells in FIGS. 12 and 13 is once again as indicated inTable 1 concerning FIG. 8.

A further embodiment of an optical grating 60 as an optical diffractioncomponent for suppressing at least one target wavelength by destructiveinterference is explained below with reference to FIGS. 14 to 16.Components and functions corresponding to those which were alreadyexplained above with reference to FIGS. 1 to 13 are denoted by the samereference signs and are not discussed in detail again.

The optical grating 60 is embodied as a superimposition of twodiffraction gratings 61, 62, which are illustrated individually in FIG.14 (diffraction grating 61) and FIG. 15 (diffraction grating 62). Thediffraction gratings 61, 62 constitute diffraction structure groups forsuppressing a respective target wavelength.

The diffraction grating 61 has a structure depth d₁ and a grating periodp₁. The diffraction grating 62 has a structure depth d₂ and a gratingperiod p₂. The two diffraction gratings 61, 62 are embodied in each caseas a binary grating.

The optical grating 60 resulting from the superimposition of the twodiffraction gratings 61, 62 has a total of three diffraction structurelevels or diffraction structure types having structure depths 0(diffraction structure level N₁), structure depth d₂ (diffractionstructure level N₂), having structure depth d₁ (diffraction structurelevel N₃) and having structure depth d₁+d₂ (diffraction structure levelN₄).

The grating periods p₁ and p₂ are identical in the case of the opticalgrating 60. The structure depths d₁, d₂ are different in the case of theoptical grating 60. In relation to a common period running direction xof the diffraction gratings 61 and 62, these two diffraction gratings 61and 62 are phase-shifted with respect to one another by one quarter ofthe common period, that is to say by p₁/4=p₂/4 with respect to oneanother.

An overlay error 63 along the period running direction x is illustratedin a dashed manner in FIGS. 15 and 16. Such an overlay error 63 can beunderstood as a phase error of the superimposition of the twodiffraction gratings 61, 62 along the period running direction and leadsto a change of extensions of the various diffraction structure levelsN₁, N₂, N₃, N₄ along the period running direction pixel x.

For the case where the two structure depths d₁ and d₂ are identical inan alternative embodiment of the optical grating 60, the two diffractionstructure levels N₂, N₃ degenerate into a common structure level, withthe result that such an optical grating consisting of two diffractiongratings having identical structure depths has exactly three diffractionstructure levels.

In the case of the optical grating 60, the surface sections of thediffraction structure groups are designated by 61 _(P) and 61 _(N).Boundary regions of the first 61 of the two binary diffraction structuregroups 61, 62 of the optical grating 60, that is to say the sidewallsbetween the levels N_(i) of the diffraction structure group 61, andboundary regions of the second 62 of the two binary diffractionstructure groups 61, 62, that is to say the level sidewalls N_(i)/N_(j)in FIG. 15, run completely separately from one another.

A further embodiment of an optical grating 60 as an optical diffractioncomponent for suppressing at least one target wavelength by destructiveinterference is explained below with reference to FIGS. 17 to 19.Components and functions corresponding to those which have already beenexplained above with reference to FIGS. 1 to 16, and particularly withreference to FIGS. 14 to 16, bear the same reference signs and will notbe discussed in detail again.

FIG. 19 shows an optical grating 64 that results as a superimposition oftwo diffraction structure groups in the form once again of diffractiongratings 65 (FIG. 17) and 66 (FIG. 18).

In the case of the diffraction gratings 65, 66 it holds true that:p ₁ =p ₂ and d ₁ =d ₂.

A phase offset of the two diffraction gratings 65, 66 with respect toone another along the period running direction x is p₁/4=p₂/4.

An extension ratio between diffraction positive structures 67, 68 of thediffraction gratings 65, 66, firstly, and the associated diffractionnegative structures 69, 70, secondly, is exactly inverted with respectto one another, with the result that the diffraction positive structures67 have the same extension along the period running direction x as thediffraction negative structures 70 of the diffraction grating 66 and thediffraction negative structures 69 of the diffraction grating 65 havethe same extension along the period running direction x as thediffraction positive structures 68 of the diffraction grating 66. Theextensions of the diffraction positive structures 67, 68, firstly, andof the diffraction negative structures 69, 70, secondly, are thus notidentical in the respective diffraction grating 65, 66, and so in thissense the two diffraction gratings 65, 66 are not binary gratings. Theextension ratio can deviate very significantly from 1:1 and isapproximately 1:3 in the case of the diffraction gratings 65, 66. Adifferent extension ratio between the diffraction positive structures67, 68, firstly, and the diffraction negative structures 69, 70,secondly, of the respective diffraction grating 65, 66 in the range ofbetween 10:1 and 1:10 is also possible.

An overlay error 63 is once again indicated in FIGS. 18 and 19. Unlikein the case of the optical grating 60, the overlay error 63 in the caseof the optical grating 64 does not lead to a change of the surface arearatios between the three diffraction structure levels N₁ (structuredepth 0), N₂ (structure depth d₁=d₂), and N₃ (structure depth d₁+d₂)along the period running direction x.

The optical grating 64 thus constitutes an optical diffraction componentincluding a periodic grating structure profile including diffractionstructures, having three diffraction structure levels (N₁ to N₃), whichpredefine different structure depths d_(i) relative to a referenceplane.

In the case of the optical grating 64, the arrangement of thediffraction structures is such that a wavelength range around a firsttarget wavelength λ₁ in the infrared wavelength range, which firsttarget wavelength is diffracted by the grating structure profile, hasradiation components having at least three different phases whichinterfere with one another destructively at least in the zero and/or +/−first order(s) of diffraction of the first target wavelength λ₁.

The diffraction structure levels N₁ to N₃ predefine a topography of agrating period of the grating structure profile that is repeatedregularly along a period running direction x. The diffraction structurelevels N₁ to N₃ include the neutral diffraction structure level N₂having a reference height of 0, the positive diffraction structure levelN₁, which is arranged higher by an optical path length of λ₁/4 relativeto the neutral diffraction structure level N₂, wherein a tolerance of+/−20% is possible for the optical path length, and the negativediffraction structure level N₃ which is arranged lower by an opticalpath length of λ₁/4+/−20% relative to the neutral diffraction structurelevel N₂.

The grating period of the grating structure profile of the opticalgrating 64 is subdivided into four period sections of the diffractionstructure levels N₁ to N₃, wherein two of the four period sections,namely the two sections having the diffraction structure level N₂, areembodied as neutral diffraction structure sections, one of the fourperiod sections, namely the period section having the diffractionstructure level N₁, is embodied as a positive diffraction structuresection and one of the four period sections, namely the period sectionhaving the diffraction structure level N₃, is embodied as a negativediffraction structure section.

These four period sections (sequence e.g. N₂, N₁, N₂, N₃) have in eachcase the same length along the period running direction x, once again atolerance range of +/−20% being possible here, too.

A further embodiment of an optical grating 60 as an optical diffractioncomponent for suppressing at least one target wavelength by destructiveinterference is explained below with reference to FIGS. 20 to 22.Components and functions corresponding to those which have already beenexplained above with reference to FIGS. 1 to 19, and particularly withreference to FIGS. 14 to 19, bear the same reference signs and will notbe discussed in detail again.

FIG. 22 shows an optical grating 71 that results as a superimposition oftwo diffraction gratings 72 (FIG. 20) and 73 (FIG. 21).

The diffraction grating 72 has a structure depth d₁ and a grating periodp₁. The diffraction grating 73 has a structure depth d₂ and a gratingperiod.

p₂=2p₁. It holds true that: d₁ d₂.

Both diffraction gratings 72, 73 are embodied as binary gratings havingan identical extension of the diffraction positive structures and of thediffractive negative structures along the period running direction x.

The optical grating 71 has four diffraction structure levels, namely N₁(structure depth 0), N₂ (structure depth d₂), N₃ (structure depth d₁)and N₄ (structure depth d₁+d₂).

FIGS. 21 and 22 once again illustrate in a dashed manner an overlayerror 63 on account of a phase offset of the two diffraction gratings72, 73 along the period running direction x.

On account of the dimensional ratios of the two diffraction gratings 72,73, the overlay errors 63, as far as the relative extensions of thediffraction structure levels N and N₂ are concerned, indeed stand outsuch that, as viewed in each case over a period p₂ of the opticalgrating 71, the ratio of extensions of the diffraction structure levelsN₁ and N₂ does not change independently of the size of the overlay error63.

On account of the dimensional ratios of the two diffraction gratings 72,73, level changes arise which are brought about by the diffractiongrating 73, respectively for one diffraction structure type of thediffraction grating 72, in this case for the diffraction positivestructures thereof. The phase relationship between the two diffractiongratings 72, 73 along the period running direction x is such thatsidewalls F of the diffraction gratings 72, 73 are not superimposed atthe same location along the period running direction x.

FIG. 23 shows, for an optical grating of the type of that of the opticalgratings 60, 64 or 71 described above with reference to FIGS. 14 to 22,the dependence of a reflectivity R of the optical grating, therespective first diffraction grating having a structure depth d₁ beingdesigned for suppressing a target wavelength of 10.6 μm by destructiveinterference, on the structure depth d₂ of the respective seconddiffraction grating from which this optical grating is constructed. Themaximum suppression of the target wavelength (reflectivity less than10⁻⁸) results for a structure depth d₂ of 2.65 μm, that is to say atapproximately one quarter of the target wavelength.

Tolerances of the structure depths and/or of the sidewall steepness aretaken into account in the associated reflectivity curve 74.

The nearer the second structure depth d₂ comes to the fixed firststructure depth d₁ of 2.65 μm, the better the suppression of the targetwavelength. An improvement in the suppression effect achieved by thefirst diffraction grating having a structure depth d₁ is already evidentin the range of the structure depth d₂ of between 0 and approximatelydouble the structure depth d₁, that is to say in the range of betweenapproximately 0.2 μm and 5 μm in FIG. 23. For the design of the twostructure depths d₁ and d₂, it becomes apparent that starting from acertain nearness of the two structure depths to one another, thesuppression effect of the two diffraction gratings having the structuredepths d₁ and d₂ is mutually reinforced. As a condition for a separationbetween the two target wavelengths λ₁ (for the first diffractiongrating) and λ₂ (for the second diffraction grating) in order that asuppression effect is mutually reinforced, the following relationshiphas been found:|λ₂−λ₁|/λ₁<0.5

Assuming that the two target wavelengths do not differ from one anotherto an excessively great extent, this condition can be written as followsindependently of whether it is related to the first wavelength λ₁ or tothe second wavelength λ₂ and without an absolute value:(λ₁−λ₂)²/(λ₁+λ₂)²<0.1

In so far as this condition is met for the two target wavelengths λ₂which are intended to be suppressed with the two diffraction gratings,that is to say the two diffraction structure groups of the opticaldiffraction component, the suppressions are mutually reinforced in thecase of the two target wavelengths λ₁, λ₂.

This is plotted in FIG. 24 as a dependence of the reflectivity on thestructure depth difference normalized to the first structure depth(d₂−d₁)/(d₁) in the value range of between −1.0 and 1.0. Between thevalues of −0.5 and 0.5 for this normalized structure depth difference,the corresponding reflectivity curve 75 is already distinctly below anasymptotic reflectivity value for larger structure depth differences.

A further embodiment of an optical grating 60 as an optical diffractioncomponent for suppressing at least one target wavelength by destructiveinterference is explained below with reference to FIGS. 25 to 28.Components and functions corresponding to those which have already beenexplained above with reference to FIGS. 1 to 24, and particularly withreference to FIGS. 14 to 22, bear the same reference signs and will notbe discussed in detail again.

FIG. 28 shows an optical grating 76 that results as a superimposition ofthree diffraction gratings 77 (FIG. 25), 78 (FIG. 26) and 79 (FIG. 27).For the structure depths d₁, d₂, d₃ of these three diffraction gratings77 to 79 it holds true that:

d₁>d₂>d₃.

The three diffraction gratings 77 to 79 are embodied in each case as abinary grating.

For the ratio of the grating periods p₁, p₂ and p₃ of the threediffraction gratings 77 to 79 it holds true that:

p₁:p₂:p₃=1:2:4.

The result is an optical diffraction component with which, in principle,three different target wavelengths can be suppressed by destructiveinterference and which includes three diffraction structure groups withthe three diffraction gratings 77 to 79. On account of this periodratio, the optical grating 76 is not sensitive to an overlay error, thatis to say in relation to a possible phase offset of the diffractionstructures of the three diffraction gratings 77 to 79 along the periodrunning direction x.

The optical grating 76 has the following eight diffraction structurelevels: N₁ (structure depth 0), N₂ (structure depth d₃), N₃ (structuredepth d₂), N₄ (structure depth d₁), N₅ (structure depth d₂+d₃), N₆(structure depth d₃+d₁), N₇ (structure depth d₁+d₂) and Ng (structuredepth d₁+d₂+d₃). These diffraction structure levels can be assigned tothe three diffraction structure groups of the three diffraction gratings77 to 79.

A further embodiment of an optical grating 60 as an optical diffractioncomponent for suppressing at least one target wavelength by destructiveinterference is explained below with reference to FIGS. 29 to 32.Components and functions corresponding to those which have already beenexplained above with reference to FIGS. 1 to 28, and particularly withreference to FIGS. 25 to 28, bear the same reference signs and will notbe discussed in detail again.

FIG. 32 shows an optical grating 80 that results from thesuperimposition of three binary diffraction gratings 81 (FIG. 29), 82(FIG. 30) and 83 (FIG. 31). For the structure depths d₁, d₂, d₃ of thethree diffraction gratings 81 to 83 it holds true that: d₁>d₂>d₃. Forthe grating periods p₁, p₂ and p₃ of the diffraction gratings 81 to 83it holds true that:

p₁:p₂:p₃=2:2:1.

An overlay error of a phase relationship between the diffractionstructures of the three diffraction gratings 81 to 83 along the periodrunning direction x, in line with what has been explained aboveconcerning the embodiments according to FIGS. 14 to 22 and 25 to 28,plays a part only in relation to the ratio between the diffractiongratings 81 and 82, since the latter have the same grating period.

The optical grating 80 also has correspondingly eight differentdiffraction structure levels which can be assigned to the threediffraction structure groups of the three diffraction gratings 81 to 83.

FIG. 33 shows, in an illustration similar to FIGS. 5 and 10, forexample, the suppression effect of an optical grating of the type of theembodiments according to FIGS. 28 and 32, including three diffractionstructure groups for suppressing three different target wavelengths.

A reflectivity curve 84 shows the wavelength-dependent suppression forthe structure depths d₁=2.65 μm, d₂=2.55 μm and d₃=2.60 μm, that is tosay embodied for suppressing the target wavelengths 10.2 μm, 10.40 μmand 10.6 μm, assuming a sidewall extension F of 0 along the periodrunning direction x, that is to say an ideally steep course of thediffraction structures of the associated diffraction gratings. Asuppression of better than 10⁻¹¹ results for the three targetwavelengths.

A reflectivity curve that in turn takes account of structure depthand/or sidewall steepness tolerances is plotted at 85 in FIG. 33. In thecase of the reflectivity curve 85, a suppression of better than 10⁻⁹results for the marginal target wavelengths 10.2 μm and 10.6 μm and asuppression in the region of 10⁻¹⁰ results for the central targetwavelength 10.40 μm.

The reflectivity curves 44 and 45 for an optical grating includingexactly two diffraction gratings and for an optical grating includingexactly one diffraction grating (cf. also FIG. 5) are depicted asreferences in FIG. 33.

FIG. 34 shows a further embodiment of an optical grating 86 as anoptical diffraction component for suppressing at least one targetwavelength by destructive interference. Components and functionscorresponding to those which have already been explained above withreference to FIGS. 1 to 33, and particularly with reference to FIGS. 4to 8, bear the same reference signs and will not be discussed in detailagain.

The optical grating 86 results as a superimposition of a total of threediffraction gratings 87, 88, 89. Two of these diffraction gratings,namely the diffraction gratings 87 and 88, have a period runningdirection x that runs horizontally in FIG. 34. The third diffractiongrating 89 has a period running direction y that runs vertically in FIG.34. In a manner similar to that in FIGS. 4 and 7, in the case of theoptical grating 86, diffraction structure types, that is to saydifferent diffraction structure levels, are highlighted by differenthatchings. If the three diffraction gratings 87 to 89 have threedifferent structure depths d₁, d₂ and d₃, the result is once again eightdifferent diffraction structure levels, corresponding to the eightdifferent types of hatching. If two of the three structure depths d₁, d₂and d₃ of the diffraction gratings 87 to 89 or else all three structuredepths are identical, the result is a correspondingly smaller number ofdifferent diffraction structure levels.

In the case of the embodiment in accordance with the optical grating 86,a suppression of the respective target wavelength is independent ofoverlay errors.

As far as the number of diffraction structure levels is concerned,reference is made to the above explanations concerning the embodimentsof the optical gratings 76 according to FIGS. 28 and 80 according toFIG. 32.

On the basis of the example of an optical diffraction component 91including three diffraction structure levels as illustrated in FIG. 35,basic properties of such diffraction components will also be explainedbelow. Components and functions corresponding to those which havealready been explained above with reference to FIGS. 1 to 34 bear thesame reference signs and will not be discussed in detail again. Thediffraction structure levels are designated by N₁, N₂ and N₃ in FIG. 35.

The target wavelength to be suppressed has a wavelength of λ_(N).

The diffraction structure level N₁ has a structure depth of 0. Thediffraction structure level N₂ has a structure depth d of λ_(N)/6. Thedeepest diffraction structure level N₃ has a structure depth of 2d(=λ_(N)/3).

A superimposition of a total of n diffraction gratings having structuredepths d₁, d₂, do is suitable for suppressing a total of n targetwavelengths λ₁, λ₂, . . . λ_(n). In this case, the number of possiblediffraction structure levels is 2^(n). Given three structure depths d₁,d₂, d₃, therefore, as explained above, eight diffraction structurelevels N₁ to N₈ result. Preferably, the various diffraction structurelevels N₁ are arranged such that all the diffraction structure levels N₁occupy identical surface area proportions of the total surface area ofthe diffraction component 91.

The optical diffraction component 91 constitutes as a variant aso-called m-level grating having in this case three levels. Such anm-level grating consists of m different diffraction structure levels,which each occupy identical surface areas and have structure heightdifferences of in each case d=λ^(N)/(2 m) with respect to one another. Agood suppression of the target wavelength λ_(N) once again results, withlower wavelength sensitivity.

The three-level grating according to FIG. 35 is assigned a gratingperiod p, according to which the sequence of the three diffractionstructure levels N₁, N₂, N₃ is repeated identically.

FIG. 36 shows a further embodiment of an optical diffraction component92 for suppressing at least one target wavelength by destructiveinterference. The illustration shows the diffraction structure levels N₁in the region around a deepest diffraction structure level N_(n), namelythe diffraction structure levels N_(n−2), N_(n−1), N_(n), N_(n+1),N_(n+2).

An intensity of reflected light in the zero order of diffraction can bewritten as follows, proceeding from the Fraunhofer approximation for thediffracted far field, in a simplified manner for an N-level, periodicphase grating:

${I(0)} = {\left| {E(0)} \right|^{2} = \left| {\sum\limits_{n = 0}^{N - 1}{L_{n}e^{{- i}\; 4\;\pi\;\frac{h_{n}}{\lambda}}}} \right|^{2}}$

In this case, I(0) is the intensity in the zero order of diffraction,that is to say the square of the absolute value of the field amplitudeof the diffracted far field.

N is the number of levels of the phase grating. L_(n) is a phase term,assigned to the respective grating level. This phase term L_(n), whichcorresponds to the extension of the respective diffraction structurelevel N_(i) along the period running direction x, is illustrated in FIG.36. h_(n) is a measure of the structure depth of the respectivediffraction structure level (cf. FIG. 36). λ is the wavelength of thediffracted light.

A further embodiment of an optical diffraction component 93 forsuppressing at least one target wavelength by destructive interferenceis explained below with reference to FIG. 37. Components and functionscorresponding to those which have already been explained above withreference to FIGS. 1 to 36, and particularly with reference to FIG. 36,bear the same reference signs and will not be discussed in detail again.

FIG. 37 shows a further embodiment of a stepped grating having identicalstructure depths of the various grating levels, designated here as h₀,and identical lengths of the diffraction structure levels N₁, N₂, N₃ andN₄ along the period running direction, designated by R in this case. Theperiod running direction R can also be the radius of a concentricdiffraction structure, wherein a centre of this diffraction structurecan coincide with a centre of the collector mirror 24.

The diffraction component 93 thus has a total of four diffractionstructure levels N₁ to N₄, the structure depths of which differ in eachcase by h₀. It holds true here that h₀=λ_(N)/4, wherein λ_(N) is thetarget wavelength to be suppressed.

One complete period p of the diffraction component in the period runningdirection R includes firstly the four descending diffraction structurelevels N₁ to N₄ and then two succeeding, reascending diffractionstructure levels N₅, N₆, wherein a structure depth of the diffractionstructure level N₅ corresponds to that of the diffraction structurelevel N₃ and a structure depth of the diffraction structure level N₆corresponds to that of the diffraction structure level N₂.

Further embodiments of optical diffraction components 94, 95 forsuppressing at least one target wavelength by destructive interferenceare described below with reference to FIGS. 38 and 39. Components andfunctions corresponding to those which have already been explained abovewith reference to FIGS. 1 to 37, and particularly with reference toFIGS. 36 and 37, bear the same reference signs and will not be discussedin detail again.

The diffraction component 94 according to FIG. 38 has, succeeding oneanother along a period running direction R within one grating period p,diffraction structure levels N₁ having a structure depth 0, N₂ having astructure depth h₁, N₃ having a structure depth h₁+h₂ and N₄ having astructure depth h₂. It holds true that: h₁<h₂.

In the case of the diffraction component 95 according to FIG. 39, alongthe period running direction R within one period p the following succeedone another: a diffraction structure level N₁ having a structure depth0, a diffraction structure level N₂ having a structure depth h₁, adiffraction structure level N₃ having a structure depth h₂ and adiffraction structure level N₄ having a structure depth h₁+h₂. Here,too, it holds true that: h₁<h₂.

Proceeding from the equation described above in association with FIG.36, an intensity in the zero order of diffraction can be specified as:

${I(0)} = \left| {1 + {\exp\left( {i\pi\frac{\lambda_{1}}{\lambda}} \right)} + {\exp\left( {i\pi\frac{\lambda_{2}}{\lambda}} \right)} + {\exp\left( {i\pi\frac{\lambda_{1} + \lambda_{2}}{\lambda}} \right)}} \right|^{2}$

In this case, λ₁ and λ₂ are the two target wavelengths which areintended to be suppressed by destructive interference via thediffraction components 94 and 95, respectively. It holds true that:h₁=λ₁/4 and h₂=λ₂/4.

For λ=λ₁ and also for λ=λ₂ it holds true that: I (0)=0. These twowavelengths are thus optimally suppressed.

Such a multilevel grating of the type of the gratings of the embodimentsin FIGS. 35 to 39 can be generalized for the suppression of a number nof target wavelengths by destructive interference. In order that nwavelengths are suppressed, 2n different diffraction structure levelsN_(i) having the following heights are used: h₁, h₂, . . . h_(n), 0,h₁+h₂, h₁+h₃, . . . , h₁+h_(n), wherein in addition the differentstructure depths h₁ to h_(n) satisfy the following relations:h ₁ <h _(i) <h _(i)+₁<2h ₁

With the optical diffraction components described above, as analternative or in addition to target wavelengths suppressed in theinfrared wavelength range, for example, wavelengths in other wavelengthranges can also be suppressed, for example in the range of DUVwavelengths.

FIG. 40 shows, in a diagram, a wavelength-dependent reflectivity R of avariant of the optical diffraction component with two structure depthsd₁ and d₂, for example of the type of the optical gratings 60, 64 or 71according to FIGS. 16, 19 and 22. In this case, structure depths presentare as follows: d₁=45 nm and d₂=52 nm. The result is a reflectivitycurve 96 shown as a solid line in FIG. 40. In addition, depicted bydashed lines are reflectivity curves 97 and 98 for corresponding opticalgratings including exactly one diffraction grating, designed with astructure depth d₁ (reflectivity curve 97) and d₂ (reflectivity curve98).

The reflectivity curve 96 shows a suppression for the two targetwavelengths λ₁≈180 nm and λ₂≈210 nm.

For the difference measure of these two target wavelengths λ₁, λ₂ itholds true that:(λ₁−λ₂)²/(λ₁+λ₂)²=0.006

The suppression at these two DUV wavelengths here is better than 10⁻⁵.

FIG. 41 shows the reflectivity R of an embodiment of an opticaldiffraction component of the type of that from FIG. 14 to 22 or 25 to32, in this case fashioned as a superimposition of a total of fourdiffraction gratings having different structure depths d₁ to d₄. Itholds true here that: d₁=45 nm, d₂=2 nm, d₃=2.55 μm and d₄=2.65 μm.

A wavelength-dependent reflectivity curve 97 shown in FIG. 41 shows,corresponding to the structure depths d₃ and d₄, two reflectivity minimawith a suppression of better than 10⁻⁶ at λ₃=10.2 μm and at λ₄=10.6 μm.

In addition, corresponding to the two structure depths d₁ and d₂, thegrating with the reflectivity curve 97 also suppresses the two DUVwavelengths λ₁≈equal to 180 nm and λ₂≈equal to 210 nm with a suppressionof better than 10⁻⁶, as shown by the magnified detail in the DUV rangein FIG. 42.

FIG. 43 illustrates, in a diagram, how, with the use of an opticaldiffraction component composed of plurality of diffraction structuregroups, the desired properties with respect to a structure depth and/orsidewall steepness tolerance are relaxed as the number of diffractionstructure groups increases. The illustration shows once again areflectivity as a function of a wavelength in the range of between 10.0and 11.0 μm. In this case, a target wavelength in the region of 10.6 μmis intended to be suppressed with a suppression of better than 10⁻⁴.

A reflectivity curve for an optical diffraction component includingexactly one diffraction structure group, that is to say includingexactly one diffraction grating, is illustrated at 98 in FIG. 43, thevalue 2.65 μm being assumed for a structure depth d, which is permittedto fluctuate within a tolerance bandwidth of 0.5%.

99 indicates a reflectivity curve for an optical diffraction componentincluding two diffraction gratings as diffraction structure groups,which have identical structure depths d₁=d₂ of 2.65 μm in each case andfor which a ten-fold tolerance bandwidth of 5% is permitted. In theregion of the target wavelength, in the case of the reflectivity curve99, a suppression results which, despite the tolerance bandwidth beingten times higher, is better than in the case of the reflectivity curve98.

In FIG. 43, 100 indicates a reflectivity curve for an opticaldiffraction component including two diffraction gratings as diffractionstructure groups, the structure depths of which are different (d₁=2.65μm, d₂=2.55 μm), a tolerance bandwidth of 3.5% being permitted in eachcase. A suppression corresponding to that of the reflectivity curve 99results at the target wavelength 10.6 μm.

In FIG. 43, 101 indicates a reflectivity curve for an opticaldiffraction component including three diffraction structure groups inthe form of three diffraction gratings having an identical structuredepth d₁=d₂=d₃ of 2.65 μm and a tolerance bandwidth of 12% for thestructure depth.

On account of the mutually reinforcing suppression effects of the threediffraction gratings in the region of the target wavelength, this veryhigh tolerance bandwidth in turn results in a very good suppressioncorresponding to the “suppression better than 10⁻⁴”.

FIG. 44 shows again the optical grating 60 including the diffractionstructure levels N₁ to N₄, as already explained above in particular withreference to FIGS. 14 to 16. FIG. 44 additionally illustrates twolithographic mask structures 105, 106, which can be used duringlithographic production of the optical grating 60.

The lithographic mask structure 105 illustrated as closest adjacent tothe optical grating 60 in FIG. 44 has mask regions 107, which areimpermeable to an etching medium, and intervening mask gaps 108, whichare permeable to the etching medium. A periodicity of the mask structure105 corresponds to that of the diffraction grating 62 according to FIG.15. The mask structure 105 defines level sidewalls N₄/N₃ between thediffraction structure levels N₄ and N₃, firstly, and N₁/N₂ between thediffraction structure levels N₁ and N₂, secondly.

Arranged offset with respect hereto along the period running direction xis the second lithographic mask structure 106 having mask regions 109and mask gaps 110. A periodicity of this second lithographic maskstructure 106 corresponds to that of the diffraction grating 61according to FIG. 14. The second lithographic mask structure 106 definesthe position of the level sidewalls N₃/N₁ between the diffractionstructure levels N₃ and N₁, firstly, and N₂/N₄ between the diffractionstructure levels N₂ and N₄, secondly.

A topography of the diffraction structure levels N₁ to N₄ of the opticalgrating 60 can be described as a superimposition of two binarystructures, namely of the diffraction structure groups 61, 62 that areproducible with the aid of the lithographic mask structures 105, 106(also cf. FIGS. 14 and 15). Each of these binary structures 61, 62 hasfirst surface sections having a first structure depth, namely thepositive structures 61 _(P), 62 _(P) of the structure groups 61, 62, andsecond surface sections having a second structure depth, namely thenegative structures 61 _(N), 62 _(N), which alternate with the firstsurface sections 61 _(P), 62 _(P) along the period running direction x.Boundary regions between these adjacent surface sections 61 _(P)/61_(N), firstly, and 62 _(P)/62 _(N), secondly, that is to say the levelsidewalls N_(i)/N_(j) explained above, of each of the binary structures61, 62 have a linear course perpendicular to the period runningdirection and perpendicular to the plane of the drawing in FIGS. 14 to16 and 44. These boundary regions N₃/N₁, N₂/N₄ of the first binarystructure 61 and the boundary regions N₄/N₃, N₁/N₂ of the second binarystructure 62 run completely separately from one another, that is to sayare not superimposed on one another in their course perpendicular to theperiod running direction x.

A further characteristic of the optical grating 60 is that, as viewedalong the period running direction x, each rising level sidewall, thatis to say

N₃/N₁, firstly, and N₄/N₃, secondly, is respectively assigned a fallinglevel sidewall of the same structure depth. In this case, the risinglevel sidewall N₃/N₁ is assigned the falling level sidewall N₂/N₄. Therising level sidewall N₄/N₃ is assigned the falling level sidewallN₁/N₂. The firstly assigned level sidewalls N₃/N₁ and N₂/N₄ in this casehave the structure depth d₁. The level sidewalls N₄/N₃ and N₁/N₂likewise assigned to one another have the structure depth d₂.

During the production of the optical grating 60, firstly one of the twomask structures 105, 106, for example the mask structure 105, is usedand, in the region of the mask gaps 108, in a first etching step usingan etching region, provided by a corresponding source, negativestructures having the width of the mask gaps 108 with a predefined firstetching depth d₂ are produced in a substrate. Afterwards, the maskstructure 105 is removed and the mask structure 106 is used and, in afurther etching step, the substrate is etched further with the depth d₁until the diffraction structure levels N₁ to N₄ corresponding to theillustration at the bottom of FIG. 44 have arisen. The mask productionof the optical grating 60 thus involves using firstly a first maskstructure for lithographically etching a substrate and then a secondmask structure, which is different with regard to the positions of maskregions and mask gaps. This difference in the position of the maskregions/mask gaps can be achieved by exchanging a first mask structurefor a further mask structure and/or by displacing a mask structure alongthe running direction x.

The production method can also include more than two etching steps andit is also possible to use more than two different mask structuresand/or more than two etching steps.

FIG. 45 shows the relations during lithographic production of theoptical grating 64 (also cf. FIGS. 17 to 19). Components and functionscorresponding to those which have already been explained above withreference to FIGS. 1 to 44, and particularly with reference to FIGS. 14to 19 and 44, bear the same reference signs and will not be discussed indetail again.

In FIG. 45, two lithographic mask structures 111, 112 are illustratedfor the optical grating 64, the mask structures once again havingperiodically successive mask regions and mask gaps. In this case, thelithographic mask structure 111 has mask regions 113 and mask gaps 114and the lithographic mask structure 112 has mask regions 115 and maskgaps 116.

During the lithographic production of the optical grating 64, thelithography mask structure 111 defines the level sidewalls N₃/N₂,firstly, and N₂/N₃, secondly, and the further lithographic maskstructure 112 defines the level sidewalls N₂/N₁, firstly, and N₁/N₂,secondly. Here, too, the optical grating 64 results as a superimpositionof two binary structures 65, 66 (cf. FIGS. 17 and 18), whose boundaryregions, that is to say the level sidewalls N_(i)/N_(j), perpendicularto the period running direction x and perpendicular to the plane of thedrawing in FIGS. 17 to 19 and 45, run completely separately, that is tosay are not superimposed on one another.

Here, too, it holds true again that, as viewed along the period runningdirection x, each rising level sidewall, that is to say the sidewallsN₂/N₁ and N₃/N₂, is once again assigned a falling level sidewall of thesame structure depth, namely the rising level sidewall N₂/N₁ is assignedthe falling level sidewall N₁/N₂, and the rising level sidewall N₃/N₂ isassigned the falling level sidewall N₂/N₃.

The optical gratings 71, 76, 80 described above in particular withreference to FIGS. 20 to 22, 25 to 28 and 29 to 32 can also be describedas a corresponding superimposition of binary structures whose boundaryregions between the surface sections, that is to say whose levelsidewalls N_(i)/N_(j), are not superimposed on one another, as alreadyexplained above with reference to the optical gratings 60 and 64. In thecase of the optical gratings 76 and 80, these can be described as asuperimposition of three binary structures whose boundary regions, thatis to say level sidewalls N_(i), N_(j), are not superimposed on oneanother. For these gratings 71, 76, 80, too, it holds true that, asviewed along the period running direction x, each rising level sidewallis assigned a falling level sidewall of the same structure depth.

In the case of the above-described optical diffraction components havingperiod running directions of the diffraction structure groups that arenot parallel to one another, this results in an intersection of thelevel sidewalls, that is to say of the boundary regions between thedifferent surface sections of the diffraction structures. In this case,too, the boundary regions are superimposed on one another only atpoints, that is to say at most along sections of the linear course ofthe level sidewalls, namely where the latter intersect.

A further embodiment of an optical diffraction component 117, once againin the form of an optical grating, for suppressing at least one targetwavelength by destructive interference is described below with referenceto FIG. 46. Components and functions corresponding to those which werealready explained above with reference to FIGS. 1 to 45 are denoted bythe same reference signs and are not discussed in detail again.

The optical grating 117 is embodied as a grating structure profile thatis periodic along the period running direction x, including diffractionstructures having three diffraction structure levels N₁, N₂, N₃.

The middle diffraction structure level N₂ predefines a reference heightof 0 (d=0) and is therefore also referred to as a neutral diffractionstructure level. The further diffraction structure level N₁ has astructure depth of d=+λ/4, measured relative to the reference height,and is therefore also referred to as a positive diffraction structurelevel. The third diffraction structure level N₃ has a structure depth ofd=−λ/4, measured relative to the reference height, and is therefore alsoreferred to as a negative diffraction structure level.

The three diffraction structure levels N₁ to N₃ thus predefine differentstructure depths relative to the reference plane d=0.

A grating period p of the grating structure profile of the opticalgrating 117 is subdivided into a total of four period sections of thediffraction structure levels N₁ to N₃. Two of these four period sectionsare embodied as the neutral diffraction structure level N₂, one of thefour period sections is embodied as the positive diffraction structurelevel N₁ and the fourth of the four period sections is embodied as thenegative diffraction structure level N₃. The sequence along the unitcell chosen in FIG. 46, the unit cell being bounded by dashed lines, inthe period running direction x is: N₂, N₁, N₂, N₃.

Along the period running direction x, the four period sections withinone grating period p have the same structure length x_(N).

Alternatively, it is also possible for the lengths of the periodsections, that is to say the x-extensions of the respective diffractionstructure levels N₁ to N₃, to differ from one another in pairs. Thefollowing should then be satisfied as a constraint for the lengthsx_(Ni) of the period sections of the diffraction structure levels N₁ toN₃:X _(N1) +X _(N3)=2x _(N2)

The sum of the extensions of the levels deviating from the neutraldiffraction structure level should thus be, to a good approximation,equal to double the extension of the neutral diffraction structurelevel.

The described arrangement, that is to say the structure depths and thelengths along the period running direction x, of the diffractionstructure levels N₁ to N₃ is such that a first target wavelength λ₁ inthe infrared wavelength range, which is diffracted by the gratingstructure profile, has radiation components having three differentphases which interfere with one another destructively in the zero orderof diffraction of the first target wavelength λ₁. A suppression effectthus results, as has been explained above inter alia in association withthe other optical diffraction components according to FIGS. 1 to 45. Asrevealed by a theoretical consideration, this suppression effect issquared in comparison with the suppression of a single binary grating(not illustrated), with the result that the optical grating 117 has asuppression effect of 10⁻⁴, for example, if a binary grating in whichpositive diffraction structure levels N₁ were in turn arranged insteadof the negative diffraction structure levels N₃ has a suppression of10⁻².

The target wavelength can once again be in the range of between 10 μmand 11 μm.

The influence of a structure depth error on the diffraction efficiencyis explained below with reference to FIGS. 47 and 48. It is assumed herethat light having the wavelength λ to be suppressed is incident on theoptical grating 117 from above with normal incidence in FIGS. 47 and 48.This assumption “normal incidence” serves merely as a model assumptionfor the following consideration. In practice, the angle of incidence ofthe light regularly deviates from normal incidence. Accordingly, thestructure depths of the optical diffraction components described hereare then adapted to the respective angle of incidence. The methods forcarrying out this design adaptation are known to the person skilled inthe art. In practice, the angles of incidence of the light vary with thewavelength to be suppressed and the structure depths of the opticaldiffraction component thus also vary over the EUV collector. In the caseof an EUV collector 24 having a rotationally symmetrical design, astructure depth of the diffraction structure groups can varycontinuously from a centre of the EUV collector 24 towards the edge ofthe EUV collector 24.

Regions of identical phase P₀ of the wave of the reflected light areillustrated by filled-in dots in FIGS. 47 and 48. Since the diffractionstructure levels N₁, firstly, and N₃, secondly, are offset relative tothe neutral diffraction structure level N₂ in each case by an opticalpath length of λ/4, it is evident that for the total of four periodsections of the grating period of the optical grating 117 illustrated inFIG. 47, in each case two regions of the reflected light result whosephase P₀ is reflected relative to two further regions in a manner offsetexactly by half a wavelength, that is to say by

λ/2, which, in the case of the perfect λ/4 structure depths in FIG. 47,leads to the perfect suppression of the incident light, that is to sayto the destructive interference of the reflected light.

FIG. 47 shows the case in which the positive diffraction structure levelN₁ has a structure depth which is greater than λ/4 and the negativediffraction structure level N₃ has a structure depth which has the sameabsolute value as the structure depth of the positive diffractionstructure level N₁, that is to say is correspondingly likewise greaterthan λ/4 in absolute terms. A height error is thus present in the caseof the grating according to FIG. 47.

Regions of identical phase P₀, d of the light reflected by the positivediffraction structure level N₁, firstly, and by the negative diffractionstructure level N₃, secondly, are illustrated by open circles in FIG.48.

As shown by the comparison of the positions in the beam direction of thereflected light of these two phases P₀, a which are reflected by thelevels N₁ and N₃, respectively, with the corresponding phase positionsP₀ in the case of the perfect suppression situation according to FIG.47, in the case of the situation according to FIG. 48 these two phasesP_(0,d) are present around the correct phase position in a mannershifted upwards and downwards, respectively, by the same distance, withthe result that an average value of the two shifted phases P_(0,d) abecomes located once again at the position of the perfect phase positionaccording to FIG. 47. This averaging brings about an improvement of thesuppression in the case of the grating having the three diffractionstructure levels N₁ to N₃ in comparison with a binary grating havingonly two diffraction structure levels corresponding to the diffractionstructure levels N₁ and N₂ and a corresponding height error.

FIG. 49 shows a further variant of an optical diffraction component forsuppressing at least one target wavelength in the form once again of anoptical grating 118 including diffraction structures, having once againthree diffraction structure levels N₁, N₂ and N₃. Components andfunctions corresponding to those which have already been explained abovewith reference to FIGS. 1 to 48, and particularly with reference toFIGS. 46 to 48, bear the same reference signs and will not be discussedin detail again.

FIG. 49 illustrates once again using dashed lines a unit cell extendingalong the period running direction x over one period p. The neutraldiffraction structure level N₂, which is present first in this unit cellin the period running direction x, has double the length 2x_(N) incomparison with the other two diffraction structure levels. The sequenceof the diffraction structure levels in the period running directionwithin the unit cell illustrated is thus: neutral diffraction structurelevel N₂ of double length 2x_(N), positive diffraction structure levelN₁ having single length x_(N), negative diffraction structure levelhaving single length x_(N). In the case of the optical grating 118,therefore, within the unit cell a positive diffraction structure levelN₁ is followed directly by a negative diffraction structure level N₃,such that an intervening level sidewall has a structure depth of λ/2.

FIG. 50 shows a further embodiment of an optical diffraction componentfor suppressing at least one target wavelength, the optical diffractioncomponent being fashioned as an optical grating 120, once againincluding diffraction structures having four diffraction structurelevels N₁ to N₄. Components and functions corresponding to those whichhave already been explained above with reference to FIGS. 1 to 49, andparticularly with reference to FIGS. 46 to 49, bear the same referencesigns and will not be discussed in detail again. Along the periodrunning direction, the optical grating 120 has the following sequence ofdiffraction structure levels: positive diffraction structure level N₁having a structure depth+λ/4, neutral diffraction structure level N₂,negative diffraction structure level N₃ having a structure depth −λ/4,doubly negative diffraction structure level N₄ having a structure depth−λ/2, negative diffraction structure level N₃ and neutral diffractionstructure level N₂. The unit cell of the optical grating 120 thusincludes the diffraction structure level sequence N₁, N₂, N₃, N₄, N₃, N₂or a corresponding cyclic interchange.

FIG. 51 shows a further embodiment of an optical diffraction componentfor suppressing at least one target wavelength, the optical diffractioncomponent being fashioned as an optical grating 121, once againincluding diffraction structures having five diffraction structurelevels N₁ to N₅. Components and functions corresponding to those whichhave already been explained above with reference to FIGS. 1 to 50, andparticularly with reference to FIGS. 46 to 50, bear the same referencesigns and will not be discussed in detail again. Along the periodrunning direction, the optical grating 121 has the following sequence ofdiffraction structure levels: positive diffraction structure level N₁having a structure depth+λ/4, neutral diffraction structure level N₂,negative diffraction structure level N₃ having a structure depth−λ/4,doubly negative diffraction structure level N₄ having a structuredepth−λ/2, triply negative diffraction structure level N₅ having astructure depth−3λ/4, doubly negative diffraction structure level N₄having a structure depth−λ/2, negative diffraction structure level N₃having a structure depth−λ/4, and neutral diffraction structure levelN₂. The unit cell of the optical grating 120 thus includes thediffraction structure level sequence N₁, N₂, N₃, N₄, N₅, N₄, N₃, N₂ or acorresponding cyclic interchange.

The additional diffraction structure levels N₄ in the case of theoptical grating 120 and N₄, N₅ in the case of the optical grating 121result in an additional reinforcement of the diffraction effect, that isto say in a further reinforcement of the destructive interference of thetarget wavelength λ.

FIG. 52 shows a reflectivity curve 125 of an optical grating of the typefrom FIG. 46 having the sequence therein of the diffraction structurelevels N₁, N₂ and N₃ having a structure depth d of in each case λ/4(d≈2.6 μm) and an identical structure length x_(N) of the diffractionstructure levels N₁ to N₃ in the period running direction x(x_(N1)=x_(N2)=x_(N3)). The result is a reflectivity curve 125 having awide reflectivity minimum at 1·10⁻⁶ around the wavelength λ=10.4 μm.Between 10.2 μm and 10.6 μm, the reflectivity is less than 2·10⁻⁶.Between 10.1 μm and 10.7 μm, the reflectivity is less than 3·10⁻⁶.Between 100 μm and 10.8 μm, the reflectivity is less than 5·10⁻⁶. Thisresults in a very good suppression of disturbing wavelengths in thewavelength ranges indicated.

FIG. 53 shows, in the manner of FIGS. 44 and 45, the relations duringlithographic production of the optical grating 64 (also cf. FIGS. 17 to19) with a period p=4x_(N).

Components and functions corresponding to those which have already beenexplained above with reference to FIGS. 1 to 52, and particularly withreference to FIGS. 14 to 19, 44 and 45, bear the same reference signsand will not be discussed in detail again.

For the optical grating 64, FIG. 53 illustrates further embodiments oflithographic mask structures 126, 127 which are used during thelithographic production of the optical grating 64 and once again haveperiodically successive mask regions and mask gaps. In this case, thelithographic mask structure 126 has successive mask regions 128 and 129and intervening mask gaps 130 and 131 and the mask structure 127 hassuccessive mask regions 132 and 133 and intervening mask gaps 134 and135.

During the lithographic production of the optical grating 64, the maskregion 128 of the mask structure 126 defines the level sidewalls N₃/N₂,firstly, and N₁/N₂, secondly. The further mask region 129 of the maskstructure 126 defines the level sidewalls N₂/N₁ and N₂/N₃ for the nextsequence of the diffraction structure levels of the optical grating 64that follows in the period running direction x. The further lithographicmask structure 127 defines, with the mask region 132, the levelsidewalls N₂/N₁ and N₂/N₃ of the period of the diffraction structurelevels N_(i) leading in the period running direction x and the maskregion 133 of the mask structure 127 defines the level sidewalls N₃/N₂and N₁/N₂ of the next period of the diffraction structure levels N_(i).The optical grating 64 correspondingly results as a superimposition oftwo binary structures whose boundary regions, perpendicular to theperiod running direction x (perpendicular to the plane of the drawing inFIG. 53) run completely separately, that is to say are not superimposedon one another.

The mask structures 128, 129, firstly, and 132, 133, secondly, have ineach case the same x-extension, namely in each case 2x_(N). The maskgaps 131, firstly, and 134, secondly, have in each case the samex-extension, namely in each case x_(N). The mask structures 130 and 135likewise have in each case the same x-extension, namely in each case3x_(N).

The mask structures 126, 127 thus predefine alternately different levelsidewalls for the respectively successive periods p of the opticalgrating 64. By shilling by a period length p, most mask structures 126and 127 can be converted into one another.

FIG. 54 shows an alternative embodiment of two mask structures 136, 137during lithographic production of the optical grating 64. Components andfunctions corresponding to those which have already been explained abovewith reference to FIGS. 1 to 53, and particularly with reference toFIGS. 14 to 19, 44 and 53, bear the same reference signs and will not bediscussed in detail again.

The mask structure 136 has mask regions 138, 139 and intervening maskgaps 140, 141. The mask structure 137 has mask regions 142, 143 andintervening mask gaps 144 and 145. An x-extension of the mask regions138, firstly, and 143, secondly, is 3x_(N) and thus three times themagnitude of an x-extension of the mask regions 139, firstly, and 142,secondly, which is x_(N). The mask gaps 140, 141, 144 and 145 have ineach case an extension of 2x_(N).

During the lithographic production of the optical grating 64, thelithographic mask structure 136 defines, with the mask region 138, thelevel sidewalk N₃/N₂ and N₂/N₃ of the first period p of the diffractionstructure levels N₁ to N₃ of the grating 64 and the mask region 139defines the level sidewalls N₂/N₁, firstly, and N₁/N₂, secondly, of thesecond period p of the diffraction structure levels N₁ to N₃. Thefurther lithographic mask structure 137 defines, with the mask region142, the level sidewalls N₂/N₁ and N₁/N₂ of the first period and, withthe mask region 143, the level sidewalls N₃/N₁ and N₂/N₃ of thesucceeding period p of the diffraction structure levels N₁ to N₃.

It holds true here, too, in a manner similar to that in the case of theembodiment according to FIG. 53, that the mask structures 136 and 137predefine alternately different level sidewalls of the successiveperiods of the diffraction structure levels N₁ to N₃. The maskstructures 136 and 137 can also be converted into one another byshifting by a period length p=4x_(N).

The relations during the production of a further embodiment of anoptical grating 146 with two mask structures 147, 148 will be describedwith reference to FIG. 55. In contrast to FIGS. 53 and 54, which eachshow two grating periods of the optical grating 64, one grating period pis shown in FIG. 55. Within this grating period p, the optical grating146 has the following sequence of the diffraction structure levels N_(i)in the running direction x: N₁, N₂, N₂, N₃ and N₂. The grating period phas an extension of 6x_(N). All diffraction levels N₁ have in each casean extension of x_(N).

The mask structure 147 has per period p mask regions 149, 150 andintervening mask gaps 151, 152 and the mask structure 148 has per periodp exactly one assigned mask region 153 and one mask gap 154. The maskregion 149 and the mask region 150 have an extension of 2x_(N). The maskgaps 151, 152 have an extension of x_(N). The mask region 153 has anextension of 3x_(N). The mask gap 154 likewise has an extension of3x_(N).

Within the sequence of the level sidewalls over the period p along theperiod running direction x, the following assignment holds true as faras the predefinition of the respective level sidewall by the mask regionof the respective mask structure is concerned:

Level Predefining sidewall mask region N₂/N₁ 153 N₁/N₂ 149 N₂/N₁ 150N₁/N₂ 153 N₂/N₃ 150 N₃/N₂ 149 N₂/N₁ 153 etc. etc.

The relations during the production of a further embodiment of anoptical grating 155 with two mask structures 156, 157 will be describedwith reference to FIG. 56. In contrast to FIGS. 53 and 54, which eachshow two grating periods of the optical grating 64, one grating period pis shown in FIG. 56. Within this grating period p, the optical grating155 has the following sequence of the diffraction structure levelsN_(i): N₂, N₁, N₂, N₃, N₂ and N₃. Thus a period p having an extension of6x_(N) is present in the case of the grating 155 as well. Thediffraction structure levels N_(i) have in each case an extension of INalong the period running direction x.

For the production of the optical grating 155, once again twolithographic mask structures 156 and 157 are illustrated in FIG. 56. Inthis case, the mask structure 156 has mask regions 158 and 159 andintervening mask gaps 160, 161 and the mask structure 157 has per periodexactly one mask region 162 and one mask gap 163. The mask regions 158and 159 have in each case the extension x_(N). The mask gaps 160, 161likewise have in each case the extension of 2x_(N). The mask region 162,firstly, and the mask gap 163, secondly, have in each case an extensionof 3x_(N).

The following holds true for the assignment of the mask regions to thelevel sidewalls during the lithographic production of the opticalgrating 155:

Level Predefining sidewall mask region N₃/N₂ 162 N₂/N₁ 158 N₁/N₂ 158N₂/N₃ 162 N₃/N₂ 159 N₂/N₃ 159 N₃/N₂ 162 etc. etc.

The above-explained structurings of the optical gratings can have theeffect that stray light radiation having an infrared wavelength, forexample, that is reflected by the EUV collector 24 interferesdestructively in a zero order and a stray light intensity is thussuppressed in the zero order. In this case, the optical diffractioncomponents described above are generally used as reflective components.

A main body of the EUV collector 24 can be manufactured from aluminium.Alternative materials for this main body are copper, alloys includingthe constituent copper and/or aluminium or alloys, produced by powdermetallurgy, of copper and aluminium oxide or silicon.

In order to produce a microstructured or nanostructured component, theprojection exposure apparatus 1 is used as follows: first, thereflection mask 10 or the reticle and the substrate or the wafer 11 areprovided. Subsequently, a structure on the reticle 10 is projected ontoa light-sensitive layer of the wafer 11 with the aid of the projectionexposure apparatus 1. Then, a microstructure or nanostructure on thewafer 11, and hence the microstructured component, is produced bydeveloping the light-sensitive layer.

What is claimed is:
 1. A component, comprising: a periodic gratingstructure profile comprising diffraction structures configured so that awavelength range around a first wavelength, λ₁, is diffracted by theperiodic grating structure profile, wherein: the first wavelength, λ₁,is in the infrared wavelength range; the wavelength range comprisesradiation components comprising at least three different phases whichinterfere with each other destructively in at least one order ofdiffraction; the at least one order of diffraction is selected from thegroup consisting of: the zero order of diffraction of the firstwavelength, λ₁; the +first order of diffraction of the first wavelength,λ₁; and the −first order of diffraction of the first wavelength, λ₁; thediffraction structures comprise diffraction structure levels; thediffraction structure levels comprise: a neutral diffraction structurelevel corresponding to a reference height of zero; a positivediffraction structure level arranged higher by an optical path length ofλ₁/4+1/−20% relative to the neutral diffraction structure level; and anegative diffraction structure level arranged lower by an optical pathlength of λ₁/4+1/−20% relative to the neutral diffraction structurelevel; and the diffraction structure levels define a topography of agrating period of a grating structure profile that is repeated regularlyalong a direction.
 2. The component of claim 1, wherein the gratingperiod comprises: a first neutral diffraction structure section havingthe neutral diffraction structure level; a second neutral diffractionstructure section having the neutral diffraction structure level; apositive diffraction structure section having the positive diffractionlevel; and a negative diffraction structure section having the negativediffraction structure level.
 3. The component of claim 2, wherein thediffraction structure sections have the following sequence: the positivediffraction structure level; the first neutral diffraction structurelevel; the negative diffraction structure level; and the second neutraldiffraction structure level.
 4. The component of claim 1, wherein, alongthe direction, the diffraction structure sections have the same lengthwithin +/−20%.
 5. The component of claim 1, wherein: the wavelengthrange further comprises a second wavelength, λ₂; the wavelength, λ₂, isdifferent from the first wavelength, λ₁; and the second wavelength, λ₂,is in the infrared wavelength range.
 6. The component of claim 5,wherein the diffraction structures are configured so that the wavelengthrange further comprises radiation components comprising at least threeadditional different phases which interfere with each otherdestructively in at least one order of diffraction selected from thegroup consisting of: the zero order of diffraction of the firstwavelength, λ₂; the +first order of diffraction of the first wavelength,λ₂; and the −first order of diffraction of the first wavelength, λ₂. 7.The component of claim 5, wherein (λ₁−λ₂)²/ (λ₁+λ₂)² <20%.
 8. Thecomponent of claim 7, wherein (λ₁−λ₂)²/(λ₁+λ₂)² >0.01%.
 9. The componentof claim 5, wherein the wavelength range comprises radiation componentscomprising at least three different phases which interfere with one eachother destructively in the zero order of diffraction of the firstwavelength, λ₂.
 10. The component of claim 5, wherein the wavelengthrange comprises radiation components comprising at least three differentphases which interfere with one each other destructively in the +firstorder of diffraction of the first wavelength, λ₂.
 11. The component ofclaim 5, wherein the wavelength range comprises radiation componentscomprising at least three different phases which interfere with one eachother destructively in the −first order of diffraction of the firstwavelength, λ₂.
 12. A component, comprising: at least three diffractionstructure levels defining different structure depths relative to areference plane, wherein: the three diffraction structure levels areassignable to at least first and second diffraction structure groups;the first diffraction structure group is configured to suppress the zeroorder of diffraction of a first wavelength, λ₁; the second diffractionstructure group is configured to suppress the zero order of diffractionof a second wavelength, λ₂; (λ₁−λ₂)²/ (λ₁+λ₂)²<20%; a topography of thediffraction structure levels comprises a superimposition of first andsecond binary diffraction structure groups; for each of the first andsecond binary diffraction structure groups: the binary diffractionstructure group comprises first surface sections having a firststructure depth and second surface sections having a second structuredepth; and the first and second surface sections alternate along adirection; boundary regions between adjacent surface sections of thefirst and second binary diffraction structure groups have a linearcourse; and boundary regions of the first binary diffraction structuregroup and boundary regions of the second binary diffraction structuregroup are superimposed on each other at most along sections of theirlinear course.
 13. The component of claim 12, wherein the boundaryregions of the first binary diffraction structure group and the boundaryregions of the second diffraction structure group run completelyseparately from one another.
 14. The component of claim 12, wherein nosections of the boundary regions of the first binary diffractionstructure group and boundary regions of the second binary diffractionstructure group are superimposed on each other.
 15. The component ofclaim 12, wherein: the first diffraction structure group comprises afirst diffraction grating supported by a grating surface; the firstdiffraction grating has a first grating period; the first diffractiongrating comprises first diffraction positive structures and firstdiffraction negative structures; the first diffraction positivestructures are perpendicular to a section of the grating surfacesurrounding the first diffraction positive structures; the firstdiffraction negative structures are perpendicular to a section of thegrating surface surrounding the first diffraction negative structures;the first diffraction grating has a first structure depth that is anoptical path difference between the first diffraction positivestructures and the first diffraction negative structures; the seconddiffraction structure group comprises a second diffraction gratingsupported by the grating surface; the second diffraction grating has asecond grating period; the second diffraction grating comprises seconddiffraction positive structures and second diffraction negativestructures; the second diffraction positive structures are perpendicularto a section of the grating surface surrounding the second diffractionpositive structures; the second diffraction negative structures areperpendicular to a section of the grating surface surrounding the seconddiffraction negative structures; and the second diffraction grating hasa second structure depth that is an optical path difference between thesecond diffraction positive structures and the second diffractionnegative structures.
 16. The component of claim 15, wherein: the firstgrating period runs along a first direction; the second grating periodruns along a second direction; and the first and second directions arenot parallel to each other.
 17. The component of claim 12, wherein thecomponent is configured so that, for the first and second diffractiongratings, surface areas of the diffraction positive structures and ofthe diffraction negative structures make identical contributions to theentire grating surface.
 18. The component of claim 12, wherein thecomponent is configured so that, for the first and second diffractiongratings, surface areas of the diffraction positive structures and ofthe diffraction negative structures make contributions to the entiregrating surface that differ by at most 20% from each other.
 19. Thecomponent of claim 12, further comprising a third diffraction gratingsupported by the grating surface.
 20. The component of claim 19,wherein: the third diffraction grating comprises third diffractionpositive structures and third diffraction negative structures; the thirddiffraction grating has a third grating period; the third diffractionpositive structures are perpendicular to a section of the gratingsurface surrounding the third diffraction positive structures; the thirddiffraction negative structures are perpendicular to a section of thegrating surface surrounding the third diffraction negative structures;the third diffraction grating has a third structure depth that is anoptical path difference between the third diffraction positivestructures and the third diffraction negative structures.
 21. Thecomponent of claim 20, wherein: the first grating period runs along afirst direction; the third grating period runs along a third direction;and the first and third directions are not run parallel to each other.22. A collector, comprising: a component according to claim 1, whereinthe collector is a lithography collector.
 23. The collector of claim 22,wherein the collector mirror is configured to guide: used radiationtoward a focal region; and radiation having the first wavelength, λ₁,away from the focal region.
 24. The collector of claim 22, wherein thecollector is an EUV lithography collector.
 25. An illumination system,comprising: a lithography collector comprising a component according toclaim 1; and an illumination optical unit configured to illuminate anobject field.
 26. An optical system, comprising: a lithography collectorcomprising a component according to claim 1; an illumination opticalunit configured to illuminate an object field; and a projection opticalunit configured to image the object field into an image field.
 27. Anapparatus, comprising: a light source; a lithography collectorcomprising a component according to claim 1; an illumination opticalunit configured to illuminate an object field; and a projection opticalunit configured to image the object field into an image field, whereinthe apparatus is a projection exposure apparatus.
 28. A method of usinga projection exposure apparatus comprising an illumination optical unitand a projection optical unit, the method comprising: using theillumination optical unit to illuminate a reticle in an object field ofthe projection optical unit; and using the projection optical unit toproject a structure of the reticle onto a light-sensitive material in animage field of the projection optical unit, wherein the illuminationoptical unit comprises a lithography collector comprising a componentaccording to claim
 1. 29. The component of claim 2, wherein: along thedirection, extensions of the diffraction structure sections differ fromeach other in pairs; and a sum of a length of the positive diffractionstructure along the direction and a length of the negative diffractionstructure along the direction is equal to two times a length of thefirst neutral diffraction structure along the direction.
 30. Thecomponent of claim 2, wherein: the positive diffraction structure levelhas a structure depth which is greater than λ₁/4; the negativediffraction structure level has a structure depth which has the sameabsolute value as the structure depth of the positive diffractionstructure level; and compared to λ₁/4, structure depth variations of thepositive diffraction structure level and of the negative diffractionstructure level are such that phases of light which are reflected by thepositive diffraction structure level and by the negative diffractionstructure level yield an average value which is located at a phaseposition of destructive interference of the reflected light.
 31. Thecomponent of claim 2, wherein the diffraction structure sections havethe following sequence: the first neutral diffraction structure level;the second neutral diffraction structure level; the positive diffractionstructure level; and the negative diffraction structure level.